CLEC11a is a bone growth agent

ABSTRACT

The present disclosure describes the C-type lectin CLEC11a as a bone growth factor. Clec11a-deficient mice showed reduced bone volume and mineralization, while bone resorption remained unchanged. Administration of recombinant Clec11a systemically promoted bone formation in mice at risk for osteoporosis.

This application is a national phase application under 35 U.S.C. § 371of International Application No. PCT/US2016/028066, filed Apr. 18, 2016,which claims benefit of priority to U.S. Provisional Application Ser.No. 62/150,071, filed Apr. 20, 2015, U.S. Provisional Application Ser.No. 62/275,570 filed Jan. 6, 2016; and U.S. Provisional Application Ser.No. 62/293,373 filed Feb. 10, 2016, the entire contents of each of whichare hereby incorporated by reference.

BACKGROUND 1. Field

The present disclosure relates generally to the fields of medicine,developmental biology and molecular biology. More particularly, itconcerns the role of CLEC11a in the generation of bone, and its use asan agent to treat bone disease.

2. Description of Related Art

Mesenchymal stem cells (MSCs), perhaps better known as skeletal stemcells (SSCs) in adult bone marrow (Bianco and Robey, 2015), aremultipotent progenitors that form fibroblast colonies in culture (CFU-F)(Friedenstein et al., 1970). These cells have the potential to give riseto stromal cells, osteoblasts, chondrocytes, and adipocytes.Nonetheless, they are not necessarily fated to form all such derivativesin vivo. Fate mapping studies show there are multiple lineages oftemporally, and perhaps spatially, distinct mesenchymal progenitors inskeletal tissues that contribute to different mesenchymal derivatives atdifferent developmental stages (Liu et al., 2013; Maes et al., 2010;Mizoguchi et al., 2014; Park et al., 2012; Takashima et al., 2007;Worthley et al., 2015; Zhou et al., 2014).

During fetal development, Osterix⁺ cells in the perichondrium give riseto osteoblasts and osteocytes in developing bones (Liu et al., 2013;Maes et al., 2010; Mizoguchi et al., 2014). In early postnatal bonemarrow, Osterix⁺ cells form stromal cells that persist throughout adultlife in the bone marrow, including Leptin Receptor (LepR)-expressingstromal cells that are the major source of bone and adipocytes in adultmice (Mizoguchi et al., 2014; Zhou et al., 2014). However, within adultbone marrow, Osterix marks only short-lived osteogenic progenitors(Mizoguchi et al., 2014; Park et al., 2012), suggesting that Osterixexpression is extinguished within LepR⁺ SSCs in adult bone marrow.Osterix⁺ osteogenic progenitors also persist periosteally, on the outersurface of adult bones, where they contribute to bone repair after boneinjuries (Maes et al., 2010).

Neural crest-derived cells transiently give rise to mesenchymalprogenitors and stromal cells in postnatal bone marrow, though thesecells are replaced by non-neural crest-derived cells in adult bonemarrow (Leucht et al., 2008; Mabuchi and Okano, 2015; Takashima et al.,2007; Zhou et al., 2014). This may explain why the contribution ofNestin-CreER-expressing cells to stroma in postnatal bone marrow(Mendez-Ferrer et al., 2010) is short-lived (Ono et al., 2014). In adultbone marrow, Nestin-CreER marks only rare stromal cells, osteoblasts,and CFU-F (Worthley et al., 2015; Zhou et al., 2014). A distinctGremlin-1-CreER-expressing lineage near the growth plate of long bonesgenerates osteoblasts, chondrocytes, and stromal cells duringdevelopment, and to a lesser extent during adulthood (Worthley et al.,2015).

Most CFU-F in adult bone marrow arise from LepR-expressing stromal cells(Zhou et al., 2014). Niches that support hematopoiesis arise throughendochondral ossification (Chan et al., 2009) and LepR⁺ bone marrowcells can form ossicles that support hematopoiesis in vivo (Zhou et al.,2014). LepR⁺ cells arise postnatally in the bone marrow and make littlecontribution to the skeleton during development, but are the majorsource of bone and adipocytes during adulthood (Zhou et al., 2014). Bonemarrow SSCs can also be identified based on the expression of CD146,CD271, VCAM-1, and Thy-1 in humans or PDGFRα, AlphaV integrin, and/orCD105 in mice, as well as the lack of expression of hematopoietic andendothelial markers (Chan et al., 2009; Chan et al., 2015; Mabuchi etal., 2013; Morikawa et al., 2009; Omatsu et al., 2010; Park et al.,2012; Sacchetti et al., 2007; Zhou et al., 2014). LepR⁺ cells are a keysource of growth factors that maintain hematopoietic stem cells (HSCs)in the bone marrow, including SCF and CXCL12 (Ding and Morrison, 2013;Ding et al., 2012; Oguro et al., 2013). Bone marrow stromal cells thatare highly enriched for CFU-F and LepR⁺ cells have also been identifiedbased on expression of high levels of Scf (Zhou et al., 2014) or Cxcl12(Ding and Morrison, 2013; Omatsu et al., 2014; Sugiyama et al., 2006) aswell as low levels of the Nestin-GFP transgene (Kunisaki et al., 2013;Mendez-Ferrer et al., 2010), PDGFR expression (Morikawa et al., 2009;Zhou et al., 2014), or Prx-1-Cre recombination (Greenbaum et al., 2013;Zhou et al., 2014).

Multiple growth factor families have been shown to promote osteogenesisincluding Wnts (Cui et al., 2011; Krishnan et al., 2006), BMPs (Nakamuraet al., 2007; Rahman et al., 2015), and IGFs (Yakar and Rosen, 2003).However, these factors have broad effects on many tissues, complicatingtheir systemic administration to promote osteogenesis. Sclerostin, a Wntsignaling inhibitor that is locally produced by the osteocytes,negatively regulates osteoblast activity and bone formation (Li et al.,2005). Consistent with this, sclerostin inhibitors promote boneformation and increase bone mineral density (McClung et al., 2014). Arecent study demonstrated that factors secreted by bone marrow SSCsstrongly promote osteogenesis (Chan et al., 2015), though the fullrepertoire of such factors remains to be identified.

Osteoporosis is a progressive bone disease characterized by decreasedbone mass and increased fracture risk (Harada and Rodan, 2003). Aging,estrogen insufficiency, long-term glucocorticoid use, and mechanicalunloading all contribute to the development of osteoporosis (Harada andRodan, 2003). Most existing osteoporosis therapies are antiresorptiveagents, such as bisphosphonates (Black et al., 1996; Liberman et al.,1995) and estrogens (Michaelsson et al., 1998), which reduce the rate ofbone loss but do not promote new bone formation. The only FDA-approvedanabolic agent that increases bone formation is Teriparatide, a smallpeptide derived from human parathyroid hormone (PTH amino acids 1-34))(Neer et al., 2001). Nonetheless, some patients cannot take Teriparatide(Kraenzlin and Meier, 2011) and its use is limited to two years becauseof a potential risk of osteosarcoma (Neer et al., 2001). Thus, thereremains a need for therapies that address bone disease, and inparticular for improved methods of stimulating bone formation andincreasing bone strength in vivo to treat bone disease and injury,including cancer.

SUMMARY

Thus, in accordance with the present disclosure, there is provided amethod of increasing bone density, strength, volume or mineralization ina subject in need thereof comprising providing to the subject CLEC11a oran agonist or mimic thereof. Also provided is a method of treating abone trauma, disease or disorder in a subject comprising providing tothe subject CLEC11a or an agonist or mimic thereof. Also provided is amethod of reversing bone loss in a subject comprising providing to thesubject CLEC11a or an agonist or mimic thereof. Also provided is amethod of promoting bone formation or osteogenesis in a subject in needthereof comprising providing to the subject CLEC11a or an agonist ormimic thereof. The osteogenesis may be promoted by mesenchymal stemcells.

The method above may be applied to a subject suffering from osteopenia,osteoporosis, bone trauma, fracture, or is in need of spinal fusion.Providing may comprise administering CLEC11a, agonist or mimic to thesubject, such as CLEC11a administered in a lipid vehicle, hydrogel ornanoparticle. Providing may comprise administering a CLEC11a agonist ormimic, such as a protein agonist or mimic, a nucleic acid agonist ormimic or a small molecule agonist or mimic. Providing may compriseadministering a CLEC11a expression cassette to the subject, such aswhere the expression cassette is comprised in a replicable vector,including a viral vector (e.g., an adenoviral vector or retroviralvector) or a non-viral vector. The viral or non-viral vector may bedelivered in or on a lipid delivery vehicle or a nanoparticle. Theexpression cassette may comprise a constitutive promoter, a globalpromoter or a bone specific promoter.

The CLEC11a or agonist or mimic thereof may be administered more thanonce, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more times. TheCLEC11a or agonist or mimic thereof may be delivered daily, weekly ormonthly. The CLEC11a or agonist or mimic thereof is may be administeredintravenously, orally, topically, subcutaneously or intra-articularly.The CLEC11a or an agonist or mimic thereof may be administeredsystemically. The CLEC11a or agonist or mimic thereof is administeredlocal to a site of bone trauma, disease or disorder.

The method may further comprise administering CLEC11a or an agonist ormimic thereof in combination with a second bone therapy, such as ananti-resportive agent (e.g., a bisphosphonate, calcitonin, denosumab,estrogen or an estrogen agonists/antagonist), or an anabolic agent(e.g., a sclerostin inhibitor or a Parathyroid Hormone (PTH) analog).The CLEC11a or CLEC11a agonist or mimic may be embedded in a slowrelease delivery vehicle, and/or a polymeric delivery vehicle. TheCLEC11a or CLEC11a agonist or mimic may be administered locally (such asembedded in a slow release locally deliver vehicle for spinal fusion, orfracture repair) or it may be administered systemically (such as tosystemically promote bone formation in the context of osteoporosis).

The bone trauma, disease or disorder may be a fracture, osteoporosis,osteopenia, primary or metastatic cancer, periodontal disease, ortransplant/reconstructive surgery, such as spinal fusion. The subjectmay be a human, a non-human mammal, or an elderly human.

Also provided is a method of inhibiting pathologic bone formationcomprising administering to a subject in need thereof a CLEC11aantagonist. The subject may exhibit a specific cite of ectopic boneformation, or exhibit systemic bone formation. The pathologic boneformation may be a result of inflammation, or as a result of trauma orburn. The CLEC11a antagonist may be an siRNA, an antibody, an antisensemolecule, a decoy receptor, a small molecule inhibitor, an inhibitoryCLEC11a fragment, or a decoy receptor.

It is contemplated that any method or composition described herein canbe implemented with respect to any other method or composition describedherein.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The word “about” means plus or minus 5% ofthe stated number.

Other objects, features and advantages of the present disclosure willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating specific embodiments of the disclosure, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the disclosure will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentdisclosure. The disclosure may be better understood by reference to oneor more of these drawings in combination with the detailed descriptionof specific embodiments presented herein.

FIGS. 1A-T. Clec11a deficient mice were grossly developmentally normaland had normal hematopoiesis. (FIGS. 1A-C) Clec11a mRNA level analysisby microarray, RNA-seq and qPCR. Whole bone marrow cells, VE-Cadherin⁺bone marrow endothelial cells, bone marrow mesenchymal stromal cells(PDGFRα⁺CD45⁻Ter119⁻CD31⁻ or Scf-GFP⁺CD45⁻Ter119⁻CD31⁻) andCol2.3-GFP⁺D45⁻Ter119⁻CD31⁻ osteoblasts were sorted from enzymaticallydissociated femur bone marrow of 2 month-old mice, followed bymicroarray (FIG. 1A; left to right: whole bone marrow cells; endothelialcells; mesenchymal stromal cells; osteoblasts), RNA-seq (FIG. 1B; leftto right: whole bone marrow cells; endothelial cells; mesenchymalstromal cells) and qPCR (FIG. 1C; left to right: whole bone marrowcells; endothelial cells; mesenchymal stromal cells; osteoblasts)analysis. The statistical significance of differences in FIGS. 1A-C wasassessed using one-way ANOVAs with Dunnett's multiple comparisons tests(n=3 mice per genotype, total, from three independent experiments).(FIG. 1D) Diagram of the position of images from femur sections. (FIGS.1E and 1F) Confocal analysis of anti-Clec11a antibody staining (green)in the femur metaphysis (FIG. 1E) and diaphysis (FIG. 1F) ofClec11a^(−/−) and sex-matched littermate control mice. Growth platechondrocytes were marked by aggrecan staining. Bone was imaged by secondharmonic generation (SHG) (n=3 mice per genotype, total, from threeindependent experiments). (FIG. 1G) Representative images of 2 month-oldcontrol and Clec11a^(−/−) mice. (FIG. 1H) Body mass of 2 month-old mice(n=8 mice per genotype, total, from six independent experiments for alldata in FIGS. 1H-P). (FIG. 1I) Cellularity of the bone marrow andspleen. (FIGS. 1J-P) Flow cytometric analysis of the frequencies ofmyeloid cells (FIG. 1J), erythroid progenitors (FIG. 1K), T cells (FIG.1L), B cells (M), hematopoietic stem cells (FIG. 1N), multipotentprogenitors (FIG. 1O) and restricted progenitors (FIG. 1P) in the bonemarrow and spleen of Clec11a^(−/−) mice and sex-matched littermatecontrols. The statistical significance of differences among genotypes inFIGS. 1H-P was assessed using two-tailed Student's t tests. (FIGS. 1Q-T;circle=control; square=Clec11a^(−/−)) Competitive reconstitutionanalysis of irradiated mice transplanted with 300,000 donor bone marrowcells from Clec11a^(−/−) or littermate control mice along with 300,000recipient bone marrow cells. All mice were long-term multilineagereconstituted by donor cells (FIG. 1Q), including CD3⁺ T cells (FIG.1R), B220⁺ B cells (FIG. 1S) and Mac1⁺Gr-1⁺ myeloid cells (FIG. 1T)(n=10 recipients per genotype, total, from two independent experiments).The statistical significance of differences among genotypes was assessedusing repeated measures two-way ANOVAs with Sidak's multiple comparisonstests. Data represent mean±SD: *P<0.05, **P<0.01, ***P<0.001.

FIGS. 2A-V. Clec11a is necessary for osteogenesis in limb bones andvertebrae. (FIGS. 2A-C) MicroCT images of trabecular bone in the distalfemur metaphysis of 2 month-old (FIG. 2A), 10 month-old (FIG. 2B) and 16month-old (FIG. 2C) Clec11a^(−/−) mice and sex-matched littermatecontrols. (FIGS. 1D-I) MicroCT analysis of trabecular bone parameters(trabecular bone volume/total volume (FIG. 2D), trabecular number (FIG.2E), trabecular thickness (FIG. 2F), trabecular spacing (FIG. 2G),connectivity density (FIG. 2H) and bone mineral density (FIG. 20) in thedistal femur metaphysis of 2, 10 and 16 month-old Clec11a^(−/−) mice andsex-matched littermate controls (n=4-9 mice per genotype, total, from atleast four independent experiments). (FIGS. 2J-L) MicroCT images oftrabecular bone from the ventral L3 lumbar vertebrae of 2 month-old(FIG. 2J), 10 month-old (FIG. 2K) and 16 month-old (FIG. 2L)Clec11a^(−/−) mice and sex-matched littermate controls. (FIGS. 2M-R)MicroCT analysis of trabecular bone parameters in the ventral L3 lumbarvertebrae of 2, 10 and 16 month-old Clec11a^(−/−) mice and sex-matchedlittermate controls (n=4-9 mice per genotype, total, from at least fourindependent experiments). (FIGS. 2S-U) Representative calcein doublelabeling images (FIG. 2S) with quantification of the trabecular bonemineral apposition (FIG. 2T) and trabecular bone formation (FIG. 2U)rates in the femur metaphysis of 2 and 10 month-old mice (n=4 mice pergenotype, total, from four independent experiments). (FIG. 2V) Boneresorption analysis by measuring the deoxypyridinoline/creatinine ratioin the urine (n=4 mice per genotype, total, from four independentexperiments). The statistical significance of differences amonggenotypes was assessed using two-tailed Student's paired t tests. Datarepresent mean±SD: *P<0.05, **P<0.01, ***P<0.001.

FIGS. 3A-N. Clec11a is necessary for osteogenic differentiation. (FIGS.3A-D) Osteogenic differentiation in culture of bone marrow stromal cellsfrom femur bone marrow of Clec11^(−/−) mice and sex-matched littermatecontrols. Alkaline phosphatase staining and alizarin red staining wereperformed after 7 days (FIG. 3A and FIG. 3B) and 14 days (FIG. 3C andFIG. 3D) to quantify t osteoblast differentiation and mineralization(n=3 independent experiments). (FIG. 3E and FIG. 3F) Adipogenicdifferentiation in culture of bone marrow stromal cells from femur bonemarrow of Clec11^(−/−) mice and sex-matched littermate controls. Oil redO staining was performed after 4 days (n=3 independent experiments).(FIG. 3G and FIG. 3H) Chondrogenic differentiation in culture of bonemarrow stromal cells from femur bone marrow of Clec11^(−/−) mice andsex-matched littermate controls. Toluidine blue staining was performedafter 14 days (n=3 independent experiments). (FIGS. 3I-K) Representativeperilipin and osteopontin (OPN) staining in femur sections of 2month-old Clec11^(−/−) mice and sex-matched littermate controls (FIG. 3Iand FIG. 3J) with the number of adipocytes per mm² (FIG. 3K) (n=3 miceper genotype, total, from three independent experiments). (FIGS. 3L-N)Representative safranin O/fast green staining in femur sections of 2month-old Clec11a^(−/−) mice and sex-matched littermate controls (FIG.3L and FIG. 3M) with the number of chondrocytes per mm² (FIG. 3N) (n=3mice per genotype, total, from three independent experiments). Thestatistical significance of differences among genotypes was assessedusing two-tailed Student's t tests. Data represent mean±SD: ***P<0.001.

FIGS. 4A-J. Clec11a is necessary for bone regeneration and fracturehealing. (FIGS. 4A-B) Hematoxylin & eosin (FIG. 4A) and safranin O (FIG.4B) staining of the callus around the fracture site two weeks after bonefracture. (FIGS. 4C-D) Representative microCT snapshot images of thecallus (FIG. 4C) and cut-plane images around the fracture site (FIG. 4D)two weeks after bone fracture. (FIGS. 4E-J) MicroCT analysis oftrabecular bone volume/total volume (FIG. 4E), trabecular number (FIG.4F), trabecular thickness (FIG. 4G), connectivity density (FIG. 4H),trabecular spacing (FIG. 4I) and bone mineral density (FIG. 4J) in thecallus two weeks after bone fracture (n=3 mice per genotype, total, fromthree independent experiments). The statistical significance ofdifferences was assessed using two-tailed Student's t tests. Datarepresent mean±SD: *P<0.05, **P<0.01.

FIGS. 5A-K. Recombinant Clec11a promotes osteogenesis in vitro and invivo. (FIGS. 5A-B) Osteogenic differentiation of stromal cells fromfemur bone marrow of wild-type mice. Vehicle or 10 ng/ml rClec11a wereadded to osteogenic culture conditions and alizarin red staining wasassessed 14 days later to test whether Clec11a would promoteosteogenesis (n=3 independent experiments with duplicate cultures pertreatment per experiment). (FIGS. 5C-D) MC3T3-E1 cells expressing emptyvector or mouse Clec11a cDNA were subjected to osteogenicdifferentiation for 14 days (n=3 independent experiments with duplicatecultures per treatment per experiment). (FIG. 5E) Representative microCTimages of trabecular bone in the distal femur metaphysis of wild-typemice treated with daily subcutaneous doses of rClec11a for 28 days(FIGS. 5E-K reflect n=4 mice per treatment, total, from four independentexperiments). (FIGS. 5F-I) MicroCT analysis of trabecular boneparameters from the distal femur metaphysis of mice treated with dailysubcutaneous doses of rClec11a for 28 days. (FIG. 5J) Trabecular boneformation rate in the femur metaphysis of mice treated with rClec11a for28 days by calcein double labeling. (FIG. 5K) Bone resorption analysisbased on the deoxypyridinoline/creatinine ratio in the urine. Thestatistical significance of differences among treatments was assessedusing one-way ANOVAs with Tukey's multiple comparisons tests. Datarepresent mean±SD: *P<0.05, **P<0.01, ***P<0.001.

FIGS. 6A-I. Recombinant Clec11a prevents ovariectomy-induced bone loss(FIG. 6A) Representative microCT images of trabecular bone in the distalfemur metaphysis. Two month-old sham operated mice (Mock) orovariectomized mice (OVX) received daily subcutaneous injections withvehicle, 40 μg/kg human PTH, or 50 μg/kg rClec11a for 28 days. (FIGS.6B-E) MicroCT analysis of trabecular bone parameters in the distal femurmetaphysis of the mice from the experiment in FIG. 6A (FIGS. 6B-Ireflect n=4 mice per treatment, total, from the same four independentexperiments). (FIG. 6F) Bone resorption analysis based on thedeoxypyridinoline/creatinine ratio in the urine. (FIG. 6G)Histomorphometry analysis of osteoclast number/bone surface intrabecular bone from the distal femur metaphysis. (FIG. 6H) Trabecularbone formation rate based on calcium double labeling in the distal femurmetaphysis. (FIG. 6I) Histomorphometry analysis of osteoblastnumber/bone surface in trabecular bones from the distal femurmetaphysis. The statistical significance of differences was assessedusing one-way ANOVAs with Tukey's multiple comparisons tests. Datarepresent mean±SD: *P<0.05, **P<0.01, ***P<0.001.

FIGS. 7A-I. Recombinant Clec11a prevents dexamethasone-induced bone loss(FIG. 7A) Representative microCT images of trabecular bone in the distalfemur metaphysis. Two month-old wild-type mice were treated with dailyintraperitoneal injections of PBS or 20 mg/kg dexamethasone (DEX) for 28days, with or without daily subcutaneous injections of vehicle, 40 μg/kghuman PTH, or 50 μg/kg rClec11a. (FIGS. 7B-E) MicroCT analysis oftrabecular bone parameters of mice from the same experiments (FIGS. 7B-Ireflect n=4 mice per treatment, total, from four independentexperiments). (FIG. 7F) Trabecular bone formation rate based on calciumdouble labeling in the distal femur metaphysis. (FIG. 7G)Histomorphometry analysis of osteoblast number/bone surface intrabecular bone from the distal femur metaphysis. (FIG. 7H) Boneresorption analysis based on the deoxypyridinoline/creatinine ratio inthe urine. (FIG. 7I) Histomorphometry analysis of osteoclast number/bonesurface in trabecular bone from the distal femur metaphysis. Thestatistical significance of differences was assessed using one-wayANOVAs with Tukey's multiple comparisons tests. Data represent mean±SD:*P<0.05, **P<0.01, ***P<0.001.

FIGS. 8A-J. Generation of Clec11a^(−/−) mice and hematopoietic analysis,related to FIGS. 1A-T. (FIGS. 8A-B) Targeting strategy to generate aloss-of-function Clec11a allele using Crispr-Cas9 gene targetting. TwosgRNAs were designed against sequences in intron 1 and intron 2 toengineer the deletion of exon 2 (FIG. 8A), which caused a frame shiftthat created a premature stop codon in exon 3 (FIG. 8B; note that regionabove number 2 is glutamic acid rich sequence, region above and to leftof number 3 is leucine zipper region, region above 4 is C-type lctindomain). The resulting mutant protein has 76 amino acids, lacking all ofthe domains that are thought to be functionally important in Clec11a(FIG. 8B). Genotyping primer locations are marked in FIG. 8A (F: Forwardprimer; R: Reverse primer). (FIG. 8C) Genomic DNA PCR. Tail genomic DNAwas extracted from Clec11a^(+/+) and Clec11a^(−/−) mice, followed by PCRamplification using the primers indicated in FIG. 8A. The amplicons weresequenced to confirm correct targeting. (FIG. 8D) HeterozygousClec11a^(+/−) mice were intercrossed and generated expected progeny inMendelian ratios (p=0.37 by Chi-square test). (FIG. 8E) Anti-Clec11aantibody staining showed Clec11a concentrated in trabecular and corticalbone in vertebrae. Growth plate chondrocytes were marked by aggrecanstaining. Bone was imaged by second harmonic generation (SHG) (n=3independent experiments). (FIGS. 8F-H) Red blood cell (FIG. 8F), whiteblood cell (FIG. 8G) and platelet (FIG. 8H) counts in 2, 10 and 16month-old Clec11a^(−/−) and sex-matched littermate control mice (n=4-6mice per genotype, total, from at least four independent experiments).The statistical significance of differences among genotypes was assessedusing two-tailed Student's t tests. (FIGS. 8I-J) Hematopoietic colonyformation by mouse bone marrow cells in cultures supplemented withrClec11a along with 1 U/ml EPO to promote erythroid progenitor colonyformation (BRU-E; FIG. 8I) or 10 ng/ml GM-CSF to promote myeloidprogenitor colony formation (CFU-G/M/GM; FIG. 8J) (n=3 independentexperiments). The statistical significance of differences amongtreatments was assessed using one-way ANOVAs with Tukey's multiplecomparisons tests. Data represent mean±SD: *P<0.05.

FIGS. 9A-J. Cortical bone analysis in Clec11a^(−/−) mice, related toFIGS. 2A-V. (FIGS. 9A-C) Representative microCT images of cortical bonein the femur diaphysis of 2 month-old (FIG. 9A), 10 month-old (FIG. 9B)and 16 month-old (FIG. 9C) Clec11a^(−/−) mice and sex-matched littermatecontrols. (FIGS. 9D-H) MicroCT analysis of the total area (FIG. 9D),cortical area (FIG. 9E), cortical area/total area (FIG. 9F), corticalthickness (FIG. 9G) and cortical bone mineral density (FIG. 9H) in thefemur diaphysis (n=4-9 mice per genotype, total, from at least fourindependent experiments). (FIGS. 9I-J) Biomechanical tests of the peakload (FIG. 9I) and fracture energy (FIG. 9J) in the femur diaphysis(n=4-9 mice per genotype, total, from at least four independentexperiments). The statistical significance of differences was assessedusing two-tailed Student's paired t tests. Data represent mean±SD:*P<0.05.

FIGS. 10A-F. Cortical bone analysis in mice wild-type mice treated withrClec11a, related to FIGS. 5A-K. (FIG. 10A) Representative microCTimages of cortical bone in the femur diaphysis of 2 month-old wild-typemice injected with vehicle or various doses of rClec11a. (FIGS. 10B-F)MicroCT analysis of the total area (FIG. 10B), cortical area (FIG. 10C),cortical area/total area (FIG. 10D), cortical thickness (FIG. 10E) andcortical bone mineral density (FIG. 10F) in the femur diaphysis (n=4mice per genotype, total, from four independent experiments). Thestatistical significance of differences was assessed using one-wayANOVAs with Tukey's multiple comparisons tests.

FIGS. 11A-F. Cortical bone analysis in ovariectomized mice, related toFIGS. 6A-I. (FIG. 11A) Representative microCT images of cortical bone inthe femur diaphysis. Two month-old sham operation mice (Mock) orovariectomized mice (OVX) were injected with vehicle, 40 μg/kg human PTH(1-34) or 50 μg/kg rClec11a for 28 days. (FIGS. 11B-F) MicroCT analysisof the total area (FIG. 11B), cortical area (FIG. 11C), corticalarea/total area (FIG. 11D), cortical thickness (FIG. 11E) and corticalbone mineral density (FIG. 11F) in the femur diaphysis (n=4 mice pergenotype, total, from four independent experiments). The statisticalsignificance of differences was assessed using one-way ANOVAs withTukey's multiple comparisons tests. Data represent mean±SD: *P<0.05,**P<0.01.

FIGS. 12A-J. Hematopoietic and cortical bone analysis in ovariectomizedmice, related to FIGS. 7A-I. (FIGS. 12A-D) White blood cell (FIG. 12A),neutrophil (FIG. 12B), lymphocyte (FIG. 12C) and monocyte (FIG. 12D)counts in two month-old wild-type mice treated with dailyintraperitoneal injections of PBS or 20 mg/kg dexamethasone (DEX) for 28days, with or without daily subcutaneous injections of vehicle, 40 μg/kghuman PTH, or 50 μg/kg rClec11a. (FIG. 12E) Representative microCTimages of cortical bone in the femur diaphysis of the same mice. (FIGS.12F-J) MicroCT analysis of the total area (FIG. 12F), cortical area(FIG. 12G), cortical area/total area (FIG. 12H), cortical thickness(FIG. 12I) and cortical bone mineral density (FIG. 12J) in the femurdiaphysis of the mice in this experiment (n=4 mice per genotype, total,from four independent experiments). The statistical significance ofdifferences among treatments was assessed using one-way ANOVAs withTukey's multiple comparisons tests. Data represent mean±SD: **P<0.01,***P<0.001.

FIGS. 13A-F. Administration of recombinant Clec11a after the onset ofovariectomy-induced osteoporosis reverses bone loss. (FIG. 13A)Representative microCT images of trabecular bone in the distal femurmetaphysis. Two month-old sham operated mice (Mock) or ovariectomizedmice (OVX) were left untreated for 28 days, then received dailysubcutaneous injections with vehicle, 40 μg/kg human PTH, 50 μg/kgrecombinant Clec11a (rClec11a) or 40 μg/kg human PTH plus 50 μg/kgrClec11a for 28 days. (FIGS. 13B-E) MicroCT analysis of trabecular bonevolume/total volume (FIG. 13B), trabecular number (FIG. 13C), trabecularthickness (FIG. 13D), trabecular spacing (FIG. 13E) and trabecular bonemineral density (FIG. 13F) in the distal femur metaphysis of the micefrom the experiment in FIG. 13A (FIGS. 13B-I reflect n=4 mice pertreatment, total, from four independent experiments).

FIGS. 14A-D. Recombinant human Clec11a promotes bone formation by humanbone marrow stromal cells in culture (hMSCs). (FIGS. 14A-D) Osteogenicdifferentiation of hMSCs in culture. Vehicle or 10 ng/ml recombinanthuman Clec11a were added to cultures. Alkaline phosphatase staining andalizarin red staining were performed after 8 days (FIGS. 14A-B) and 21days (FIGS. 14C-D) to quantify osteogenic differentiation andmineralization (n=3 independent experiments).

FIGS. 15A-B. rhClec11a promotes bone formation by hMSCs in vivo. (FIGS.15A and 15B) In vivo transplantation of hMSCs in NSG mice. hMSCs weremixed with 40 mg of HA/TCP particles with vehicle or 10 ng/ml rhClec11afor 2 hours at 37° C., and then embedded in fibrin gels and transplantedsubcutaneously into NSG mice. Vehicle or 50 μg/kg rhClec11a weresubcutaneously injected daily for 4 weeks before the ossicles weredissected and sectioned for H&E staining (n=4 independent experiments).ft, fibrous tissue. hac, HA/TCP carrier. At this time point, little bone(pink) was observed in mice injected with vehicle, but extensive bonewas observed in mice injected with rhClec11a.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As discussed above, bone trauma and bone diseases/disorders are a majorhealth issue, and in particular for the aging population. Here, theinventors have identified CLEC11a, a poorly understood C-type lectinpreviously implicated in hematopoiesis, as an important regulator ofbone growth and mineralization. In contrast to earlier reports, theinventors observed little hematopoietic effect in vitro from theaddition of CLEC11a. Moreover, Clec11a-deficient mice showed reducedbone formation, but no changes in bone resorption and no changes inhematopoiesis within normal mice. Therefore, CLEC11a is proposed as abone growth factor that promotes osteogenesis in vivo. These and otheraspects of the disclosure are described in detail below

I. CLEC11A

C-type lectin domain family 11 member A, also known as Stem Cell GrowthFactor (SCGF), is a protein that in humans is encoded by the CLEC11Agene. This gene encodes a member of the C-type lectin superfamily. It isa secreted sulfated glycoprotein that can promote colony formation byhuman hematopoietic progenitors in culture (Bannwarth et al., 1999;Bannwarth et al., 1998; Hiraoka et al., 1997; Mio et al., 1998). Theplasma level of human Clec11a correlates with hemoglobin level (Kelleret al., 2009; Ouma et al., 2010) and increases in patients after bonemarrow transplantation (Ito et al., 2003). As a result, Clec11a has beenconsidered a hematopoietic growth factor. However, Clec11 is alsoexpressed in skeletal tissues (Hiraoka et al., 2001) and thephysiological function of Clec11a in vivo has not yet been tested.

The encoded protein is a secreted sulfated glycoprotein. An alternativesplice variant has been described but its biological nature has not beendetermined. The mRNA sequence can be found at accession no. NM_002975(SEQ ID NO: 9), and the protein sequence can be found at accession no.NP_002966 (SEQ ID NO: 10). SCGF has been disclosed in the context ofwound healing, tissue regeneration, stimulating implant fixation andangiogenesis (see, e.g., U.S. Patent Publication 2005/0066266).Antagonists of SCGF were proposed for treating atherosclerosis, tumorsand scarring are also disclosed.

In certain embodiments, expression cassettes are employed to expressCLEC11a. Expression requires that appropriate signals be provided in thevectors, and include various regulatory elements such asenhancers/promoters from both viral and mammalian sources that driveexpression of the genes of interest in cells. Elements designed tooptimize messenger RNA stability and translatability in host cells alsoare defined. The conditions for the use of a number of dominant drugselection markers for establishing permanent, stable cell clonesexpressing the products are also provided, as is an element that linksexpression of the drug selection markers to expression of thepolypeptide. Thus, reference to provision or administration of CLEC11a,as set forth herein, should be interpreted as including provision ofboth CLEC11a protein and nucleic acid sequences coding therefor.

A. Regulatory Elements

Throughout this application, the term “expression cassette” is meant toinclude any type of genetic construct containing a nucleic acid codingfor a gene product in which part or all of the nucleic acid encodingsequence is capable of being transcribed and translated, i.e., is underthe control of a promoter. A “promoter” refers to a DNA sequencerecognized by the synthetic machinery of the cell, or introducedsynthetic machinery, required to initiate the specific transcription ofa gene. The phrase “under transcriptional control” means that thepromoter is in the correct location and orientation in relation to thenucleic acid to control RNA polymerase initiation and expression of thegene. An “expression vector” is meant to include expression cassettescomprised in a genetic construct that is capable of replication, andthus including one or more of origins of replication, transcriptiontermination signals, poly-A regions, selectable markers, andmultipurpose cloning sites.

The term promoter will be used here to refer to a group oftranscriptional control modules that are clustered around the initiationsite for RNA polymerase II. Much of the thinking about how promoters areorganized derives from analyses of several viral promoters, includingthose for the HSV thymidine kinase (tk) and SV40 early transcriptionunits. These studies, augmented by more recent work, have shown thatpromoters are composed of discrete functional modules, each consistingof approximately 7-20 bp of DNA, and containing one or more recognitionsites for transcriptional activator or repressor proteins.

At least one module in each promoter functions to position the startsite for RNA synthesis. The best known example of this is the TATA box,but in some promoters lacking a TATA box, such as the promoter for themammalian terminal deoxynucleotidyl transferase gene and the promoterfor the SV40 late genes, a discrete element overlying the start siteitself helps to fix the place of initiation.

Additional promoter elements regulate the frequency of transcriptionalinitiation. Typically, these are located in the region 30-110 bpupstream of the start site, although a number of promoters have recentlybeen shown to contain functional elements downstream of the start siteas well. The spacing between promoter elements frequently is flexible,so that promoter function is preserved when elements are inverted ormoved relative to one another. In the tk promoter, the spacing betweenpromoter elements can be increased to 50 bp apart before activity beginsto decline. Depending on the promoter, it appears that individualelements can function either co-operatively or independently to activatetranscription.

In certain embodiments, viral promotes such as the human cytomegalovirus(CMV) immediate early gene promoter, the SV40 early promoter, the Roussarcoma virus long terminal repeat, rat insulin promoter andglyceraldehyde-3-phosphate dehydrogenase can be used to obtainhigh-level expression of the coding sequence of interest. The use ofother viral or mammalian cellular or bacterial phage promoters which arewell-known in the art to achieve expression of a coding sequence ofinterest is contemplated as well, provided that the levels of expressionare sufficient for a given purpose. By employing a promoter withwell-known properties, the level and pattern of expression of theprotein of interest following transfection or transformation can beoptimized. Further, selection of a promoter that is regulated inresponse to specific physiologic signals can permit inducible expressionof the gene product.

Enhancers are genetic elements that increase transcription from apromoter located at a distant position on the same molecule of DNA.Enhancers are organized much like promoters. That is, they are composedof many individual elements, each of which binds to one or moretranscriptional proteins. The basic distinction between enhancers andpromoters is operational. An enhancer region as a whole must be able tostimulate transcription at a distance; this need not be true of apromoter region or its component elements. On the other hand, a promotermust have one or more elements that direct initiation of RNA synthesisat a particular site and in a particular orientation, whereas enhancerslack these specificities. Promoters and enhancers are often overlappingand contiguous, often seeming to have a very similar modularorganization.

Below is a list of promoters/enhancers and inducible promoters/enhancersthat could be used in combination with the nucleic acid encoding a geneof interest in an expression construct (Table 1 and Table 2).Additionally, any promoter/enhancer combination (as per the EukaryoticPromoter Data Base EPDB) could also be used to drive expression of thegene. Eukaryotic cells can support cytoplasmic transcription fromcertain bacterial promoters if the appropriate bacterial polymerase isprovided, either as part of the delivery complex or as an additionalgenetic expression construct.

TABLE 1 Promoter and/or Enhancer Promoter/Enhancer ReferencesImmunoglobulin Heavy Banerji et al., 1983; Gilles et al., 1983; ChainGrosschedl et al., 1985; Atchinson et al., 1986, 1987; Imler et al.,1987; Weinberger et al., 1984; Kiledjian et al., 1988; Porton et al.;1990 Immunoglobulin Light Queen et al., 1983; Picard et al., 1984 ChainT-Cell Receptor Luria et al., 1987; Winoto et al., 1989; Redondo et al.;1990 HLA DQ a and/or DQ β Sullivan et al., 1987 β-Interferon Goodbournet al., 1986; Fujita et al., 1987; Goodbourn et al., 1988 Interleukin-2Greene et al., 1989 Interleukin-2 Receptor Greene et al., 1989; Lin etal., 1990 MHC Class II 5 Koch et al., 1989 MHC Class II HLA-DRa Shermanet al., 1989 β-Actin Kawamoto et al., 1988; Ng et al.; 1989 MuscleCreatine Kinase Jaynes et al., 1988; Horlick et al., 1989; (MCK) Johnsonet al., 1989 Prealbumin Costa et al., 1988 (Transthyretin) Elastase IOrnitz et al., 1987 Metallothionein (MTII) Karin et al., 1987; Culottaet al., 1989 Collagenase Pinkert et al., 1987; Angel et al., 1987aAlbumin Pinkert et al., 1987; Tronche et al., 1989, 1990 α-FetoproteinGodbout et al., 1988; Campere et al., 1989 t-Globin Bodine et al., 1987;Perez-Stable et al., 1990 β-Globin Trudel et al., 1987 c-fos Cohen etal., 1987 c-HA-ras Triesman, 1986; Deschamps et al., 1985 Insulin Edlundet al., 1985 Neural Cell Adhesion Hirsh et al., 1990 Molecule (NCAM)α₁-Antitrypain Latimer et al., 1990 H2B (TH2B) Histone Hwang et al.,1990 Mouse and/or Type I Ripe et al., 1989 Collagen Glucose-RegulatedChang et al., 1989 Proteins (GRP94 and GRP78) Rat Growth Hormone Larsenet al., 1986 Human Serum Amyloid Edbrooke et al., 1989 A (SAA) TroponinI (TN I) Yutzey et al., 1989 Platelet-Derived Growth Pech et al., 1989Factor (PDGF) Duchenne Muscular Klamut et al., 1990 Dystrophy SV40Banerji et al., 1981; Moreau et al., 1981; Sleigh et al., 1985; Firak etal., 1986; Herr et al., 1986; Imbra et al., 1986; Kadesch et al., 1986;Wang et al., 1986; Ondek et al., 1987; Kuhl et al., 1987; Schaffner etal., 1988 Polyoma Swartzendruber et al., 1975; Vasseur et al., 1980;Katinka et al., 1980, 1981; Tyndell et al., 1981; Dandolo et al., 1983;de Villiers et al., 1984; Hen et al., 1986; Satake et al., 1988;Campbell and/or Villarreal, 1988 Retroviruses Kriegler et al., 1982,1983; Levinson et al., 1982; Kriegler et al., 1983, 1984a, b, 1988;Bosze et al., 1986; Miksicek et al., 1986; Celander et al., 1987;Thiesen et al., 1988; Celander et al., 1988; Choi et al., 1988; Reismanet al., 1989 Papilloma Virus Campo et al., 1983; Lusky et al., 1983;Spandidos and/or Wilkie, 1983; Spalholz et al., 1985; Lusky et al.,1986; Cripe et al., 1987; Gloss et al., 1987; Hirochika et al., 1987;Stephens et al., 1987 Hepatitis B Virus Bulla et al., 1986; Jameel etal., 1986; Shaul et al., 1987; Spandau et al., 1988; Vannice et al.,1988 Human Immunodefi- Muesing et al., 1987; Hauber et al., 1988; ciencyVirus Jakobovits et al., 1988; Feng et al., 1988; Takebe et al., 1988;Rosen et al., 1988; Berkhout et al., 1989; Laspia et al., 1989; Braddocket al., 1989 Cytomegalovirus (CMV) Weber et al., 1984; Boshart et al.,1985; Foecking et al., 1986 Gibbon Ape Leukemia Holbrook et al., 1987;Quinn et al., 1989 Virus

TABLE 2 Inducible Elements Element Inducer References MT II PhorbolEster (TFA) Palmiter et al., 1982; Heavy metals Haslinger et al., 1985;Searle et al., 1985; Stuart et al., 1985; Imagawa et al., 1987, Karin etal., 1987; Angel et al., 1987b; McNeall et al., 1989 MMTV (mouseGlucocorticoids Huang et al., 1981; Lee et mammary tumor al., 1981;Majors et al., virus) 1983; Chandler et al., 1983; Ponta et al., 1985;Sakai et al., 1988 β-Interferon poly(rI)x poly(rc) Tavernier et al.,1983 Adenovirus 5 E2 ElA Imperiale et al., 1984 Collagenase PhorbolEster (TPA) Angel et al., 1987a Stromelysin Phorbol Ester (TPA) Angel etal., 1987b SV40 Phorbol Ester (TPA) Angel et al., 1987b Murine MX GeneInterferon, Newcastle Hug et al., 1988 Disease Virus GRP78 Gene A23187Resendez et al., 1988 α-2-Macroglobulin IL-6 Kunz et al., 1989 VimentinSerum Rittling et al., 1989 MHC Class I Gene Interferon Blanar et al.,1989 H-2κb HSP70 ElA, SV40 Large T Taylor et al., 1989, 1990a, Antigen1990b Proliferin Phorbol Ester-TPA Mordacq et al., 1989 Tumor NecrosisPMA Hensel et al., 1989 Factor Thyroid Stimulating Thyroid HormoneChatterjee et al., 1989 Hormone α GeneOf particular interest are bone specific or selective promoters.

Where a cDNA insert is employed, one will typically desire to include apolyadenylation signal to effect proper polyadenylation of the genetranscript. The nature of the polyadenylation signal is not believed tobe crucial to the successful practice of the disclosure, and any suchsequence may be employed such as human growth hormone and SV40polyadenylation signals. Also contemplated as an element of theexpression cassette is a terminator. These elements can serve to enhancemessage levels and to minimize read through from the cassette into othersequences.

B. Multigene Constructs and IRES

In certain embodiments of the disclosure, the use of internal ribosomebinding sites (IRES) elements are used to create multigene, orpolycistronic, messages. IRES elements are able to bypass the ribosomescanning model of 5′ methylated Cap dependent translation and begintranslation at internal sites (Pelletier and Sonenberg, 1988). IRESelements from two members of the picanovirus family (polio andencephalomyocarditis) have been described (Pelletier and Sonenberg,1988), as well as an IRES from a mammalian message (Macejak and Sarnow,1991). IRES elements can be linked to heterologous open reading frames.Multiple open reading frames can be transcribed together, each separatedby an IRES, creating polycistronic messages. By virtue of the IRESelement, each open reading frame is accessible to ribosomes forefficient translation. Multiple genes can be efficiently expressed usinga single promoter/enhancer to transcribe a single message.

Any heterologous open reading frame can be linked to IRES elements. Thisincludes genes for secreted proteins, multi-subunit proteins, encoded byindependent genes, intracellular or membrane-bound proteins andselectable markers. In this way, expression of several proteins can besimultaneously engineered into a cell with a single construct and asingle selectable marker.

C. Delivery of Expression Vectors

There are a number of ways in which expression vectors may be introducedinto cells. In certain embodiments of the disclosure, the expressionconstruct comprises a virus or engineered construct derived from a viralgenome. The ability of certain viruses to enter cells viareceptor-mediated endocytosis, to integrate into host cell genome andexpress viral genes stably and efficiently have made them attractivecandidates for the transfer of foreign genes into mammalian cells(Ridgeway, 1988; Nicolas and Rubenstein, 1988; Baichwal and Sugden,1986; Temin, 1986). The first viruses used as gene vectors were DNAviruses including the papovaviruses (simian virus 40, bovine papillomavirus, and polyoma) (Ridgeway, 1988; Baichwal and Sugden, 1986) andadenoviruses (Ridgeway, 1988; Baichwal and Sugden, 1986). These have arelatively low capacity for foreign DNA sequences and have a restrictedhost spectrum. Furthermore, their oncogenic potential and cytopathiceffects in permissive cells raise safety concerns. They can accommodateonly up to 8 kB of foreign genetic material but can be readilyintroduced in a variety of cell lines and laboratory animals (Nicolasand Rubenstein, 1988; Temin, 1986).

One of the preferred methods for in vivo delivery involves the use of anadenovirus expression vector. “Adenovirus expression vector” is meant toinclude those constructs containing adenovirus sequences sufficient to(a) support packaging of the construct and (b) to express an antisensepolynucleotide that has been cloned therein. In this context, expressiondoes not require that the gene product be synthesized.

The expression vector comprises a genetically engineered form ofadenovirus. Knowledge of the genetic organization of adenovirus, a 36kB, linear, double-stranded DNA virus, allows substitution of largepieces of adenoviral DNA with foreign sequences up to 7 kB (Grunhaus andHorwitz, 1992). In contrast to retrovirus, the adenoviral infection ofhost cells does not result in chromosomal integration because adenoviralDNA can replicate in an episomal manner without potential genotoxicity.Also, adenoviruses are structurally stable, and no genome rearrangementhas been detected after extensive amplification. Adenovirus can infectvirtually all epithelial cells regardless of their cell cycle stage. Sofar, adenoviral infection appears to be linked only to mild disease suchas acute respiratory disease in humans.

Adenovirus is particularly suitable for use as a gene transfer vectorbecause of its mid-sized genome, ease of manipulation, high titer, widetarget cell range and high infectivity. Both ends of the viral genomecontain 100-200 base pair inverted repeats (ITRs), which are ciselements necessary for viral DNA replication and packaging. The early(E) and late (L) regions of the genome contain different transcriptionunits that are divided by the onset of viral DNA replication. The E1region (E1A and E1B) encodes proteins responsible for the regulation oftranscription of the viral genome and a few cellular genes. Theexpression of the E2 region (E2A and E2B) results in the synthesis ofthe proteins for viral DNA replication. These proteins are involved inDNA replication, late gene expression and host cell shut-off (Renan,1990). The products of the late genes, including the majority of theviral capsid proteins, are expressed only after significant processingof a single primary transcript issued by the major late promoter (MLP).The MLP, (located at 16.8 m.u.) is particularly efficient during thelate phase of infection, and all the mRNA's issued from this promoterpossess a 5′-tripartite leader (TPL) sequence which makes them preferredmRNA's for translation.

In one system, recombinant adenovirus is generated from homologousrecombination between shuttle vector and provirus vector. Due to thepossible recombination between two proviral vectors, wild-typeadenovirus may be generated from this process. Therefore, it is criticalto isolate a single clone of virus from an individual plaque and examineits genomic structure.

Generation and propagation of the current adenovirus vectors, which arereplication deficient, depend on a unique helper cell line, designated293, which was transformed from human embryonic kidney cells by Ad5 DNAfragments and constitutively expresses E1 proteins (Graham et al.,1977). Since the E3 region is dispensable from the adenovirus genome(Jones and Shenk, 1978), the current adenovirus vectors, with the helpof 293 cells, carry foreign DNA in either the E1, the D3 or both regions(Graham and Prevec, 1991). In nature, adenovirus can packageapproximately 105% of the wild-type genome (Ghosh-Choudhury et al.,1987), providing capacity for about 2 extra kb of DNA. Combined with theapproximately 5.5 kb of DNA that is replaceable in the E1 and E3regions, the maximum capacity of the current adenovirus vector is under7.5 kb, or about 15% of the total length of the vector. More than 80% ofthe adenovirus viral genome remains in the vector backbone and is thesource of vector-borne cytotoxicity. Also, the replication deficiency ofthe E1-deleted virus is incomplete.

Helper cell lines may be derived from human cells such as humanembryonic kidney cells, muscle cells, hematopoietic cells or other humanembryonic mesenchymal or epithelial cells. Alternatively, the helpercells may be derived from the cells of other mammalian species that arepermissive for human adenovirus. Such cells include, e.g., Vero cells orother monkey embryonic mesenchymal or epithelial cells. As stated above,the preferred helper cell line is 293.

Racher et al. (1995) disclosed improved methods for culturing 293 cellsand propagating adenovirus. In one format, natural cell aggregates aregrown by inoculating individual cells into 1 liter siliconized spinnerflasks (Techne, Cambridge, UK) containing 100-200 ml of medium.Following stirring at 40 rpm, the cell viability is estimated withtrypan blue. In another format, Fibra-Cel microcarriers (Bibby Sterlin,Stone, UK) (5 g/l) is employed as follows. A cell inoculum, resuspendedin 5 ml of medium, is added to the carrier (50 ml) in a 250 mlErlenmeyer flask and left stationary, with occasional agitation, for 1to 4 h. The medium is then replaced with 50 ml of fresh medium andshaking initiated. For virus production, cells are allowed to grow toabout 80% confluence, after which time the medium is replaced (to 25% ofthe final volume) and adenovirus added at an MOI of 0.05. Cultures areleft stationary overnight, following which the volume is increased to100% and shaking commenced for another 72 h.

Other than the requirement that the adenovirus vector be replicationdefective, or at least conditionally defective, the nature of theadenovirus vector is not believed to be crucial to the successfulpractice of the disclosure. The adenovirus may be of any of the 42different known serotypes or subgroups A-F. Adenovirus type 5 ofsubgroup C is the preferred starting material in order to obtain theconditional replication-defective adenovirus vector for use in thepresent disclosure. This is because Adenovirus type 5 is a humanadenovirus about which a great deal of biochemical and geneticinformation is known, and it has historically been used for mostconstructions employing adenovirus as a vector.

As stated above, the typical vector according to the present disclosureis replication defective and will not have an adenovirus E1 region.Thus, it will be most convenient to introduce the polynucleotideencoding the gene of interest at the position from which the E1-codingsequences have been removed. However, the position of insertion of theconstruct within the adenovirus sequences is not critical to thedisclosure. The polynucleotide encoding the gene of interest may also beinserted in lieu of the deleted E3 region in E3 replacement vectors, asdescribed by Karlsson et al. (1986), or in the E4 region where a helpercell line or helper virus complements the E4 defect.

Adenovirus is easy to grow and manipulate and exhibits broad host rangein vitro and in vivo. This group of viruses can be obtained in hightiters, e.g., 10⁹-10¹² plaque-forming units per ml, and they are highlyinfective. The life cycle of adenovirus does not require integrationinto the host cell genome. The foreign genes delivered by adenovirusvectors are episomal and, therefore, have low genotoxicity to hostcells. No side effects have been reported in studies of vaccination withwild-type adenovirus (Couch et al., 1963; Top et al., 1971),demonstrating their safety and therapeutic potential as in vivo genetransfer vectors.

Adenovirus vectors have been used in eukaryotic gene expression (Levreroet al., 1991; Gomez-Foix et al., 1992) and vaccine development (Grunhausand Horwitz, 1992; Graham and Prevec, 1991). Recently, animal studiessuggested that recombinant adenovirus could be used for gene therapy(Stratford-Perricaudet and Perricaudet, 1991; Stratford-Perricaudet etal., 1990; Rich et al., 1993). Studies in administering recombinantadenovirus to different tissues include trachea instillation (Rosenfeldet al., 1991; Rosenfeld et al., 1992), muscle injection (Ragot et al.,1993), peripheral intravenous injections (Herz and Gerard, 1993) andstereotactic inoculation into the brain (Le Gal La Salle et al., 1993).

The retroviruses are a group of single-stranded RNA virusescharacterized by an ability to convert their RNA to double-stranded DNAin infected cells by a process of reverse-transcription (Coffin, 1990).The resulting DNA then stably integrates into cellular chromosomes as aprovirus and directs synthesis of viral proteins. The integrationresults in the retention of the viral gene sequences in the recipientcell and its descendants. The retroviral genome contains three genes,gag, pol, and env that code for capsid proteins, polymerase enzyme, andenvelope components, respectively. A sequence found upstream from thegag gene contains a signal for packaging of the genome into virions. Twolong terminal repeat (LTR) sequences are present at the 5′ and 3′ endsof the viral genome. These contain strong promoter and enhancersequences and are also required for integration in the host cell genome(Coffin, 1990).

In order to construct a retroviral vector, a nucleic acid encoding agene of interest is inserted into the viral genome in the place ofcertain viral sequences to produce a virus that isreplication-defective. In order to produce virions, a packaging cellline containing the gag, pol, and env genes but without the LTR andpackaging components is constructed (Mann et al., 1983). When arecombinant plasmid containing a cDNA, together with the retroviral LTRand packaging sequences is introduced into this cell line (by calciumphosphate precipitation for example), the packaging sequence allows theRNA transcript of the recombinant plasmid to be packaged into viralparticles, which are then secreted into the culture media (Nicolas andRubenstein, 1988; Temin, 1986; Mann et al., 1983). The media containingthe recombinant retroviruses is then collected, optionally concentrated,and used for gene transfer. Retroviral vectors are able to infect abroad variety of cell types. However, integration and stable expressionrequire the division of host cells (Paskind et al., 1975).

A novel approach designed to allow specific targeting of retrovirusvectors was recently developed based on the chemical modification of aretrovirus by the chemical addition of lactose residues to the viralenvelope. This modification could permit the specific infection ofhepatocytes via sialoglycoprotein receptors.

A different approach to targeting of recombinant retroviruses wasdesigned in which biotinylated antibodies against a retroviral envelopeprotein and against a specific cell receptor were used. The antibodieswere coupled via the biotin components by using streptavidin (Roux etal., 1989). Using antibodies against major histocompatibility complexclass I and class II antigens, they demonstrated the infection of avariety of human cells that bore those surface antigens with anecotropic virus in vitro (Roux et al., 1989).

There are certain limitations to the use of retrovirus vectors in allaspects of the present disclosure. For example, retrovirus vectorsusually integrate into random sites in the cell genome. This can lead toinsertional mutagenesis through the interruption of host genes orthrough the insertion of viral regulatory sequences that can interferewith the function of flanking genes (Varmus et al., 1981). Anotherconcern with the use of defective retrovirus vectors is the potentialappearance of wild-type replication-competent virus in the packagingcells. This can result from recombination events in which theintact-sequence from the recombinant virus inserts upstream from thegag, pol, env sequence integrated in the host cell genome. However, newpackaging cell lines are now available that should greatly decrease thelikelihood of recombination (Markowitz et al., 1988; Hersdorffer et al.,1990).

Other viral vectors may be employed as expression constructs in thepresent disclosure. Vectors derived from viruses such as vaccinia virus(Ridgeway, 1988; Baichwal and Sugden, 1986; Coupar et al., 1988)adeno-associated virus (AAV) (Ridgeway, 1988; Baichwal and Sugden, 1986;Hermonat and Muzycska, 1984) and herpesviruses may be employed. Theyoffer several attractive features for various mammalian cells(Friedmann, 1989; Ridgeway, 1988; Baichwal and Sugden, 1986; Coupar etal., 1988; Horwich et al., 1990).

In order to effect expression of sense or antisense gene constructs, theexpression construct must be delivered into a cell. This delivery may beaccomplished in vitro, as in laboratory procedures for transformingcells lines, or in vivo or ex vivo, as in the treatment of certaindisease states. One mechanism for delivery is via viral infection wherethe expression construct is encapsidated in an infectious viralparticle.

Several non-viral methods for the transfer of expression constructs intocultured mammalian cells also are contemplated by the presentdisclosure. These include calcium phosphate precipitation (Graham andVan Der Eb, 1973; Chen and Okayama, 1987; Rippe et al., 1990)DEAE-dextran (Gopal, 1985), electroporation (Tur-Kaspa et al., 1986;Potter et al., 1984), direct microinjection (Harland and Weintraub,1985), DNA-loaded liposomes (Nicolau and Sene, 1982; Fraley et al.,1979) and lipofectamine-DNA complexes, cell sonication (Fechheimer etal., 1987), gene bombardment using high velocity microprojectiles (Yanget al., 1990), and receptor-mediated transfection (Wu and Wu, 1987; Wuand Wu, 1988). Some of these techniques may be successfully adapted forin vivo or ex vivo use.

Once the expression construct has been delivered into the cell thenucleic acid encoding the gene of interest may be positioned andexpressed at different sites. In certain embodiments, the nucleic acidencoding the gene may be stably integrated into the genome of the cell.This integration may be in the cognate location and orientation viahomologous recombination (gene replacement) or it may be integrated in arandom, non-specific location (gene augmentation). In yet furtherembodiments, the nucleic acid may be stably maintained in the cell as aseparate, episomal segment of DNA. Such nucleic acid segments or“episomes” encode sequences sufficient to permit maintenance andreplication independent of or in synchronization with the host cellcycle. How the expression construct is delivered to a cell and where inthe cell the nucleic acid remains is dependent on the type of expressionconstruct employed.

In yet another embodiment of the disclosure, the expression constructmay simply consist of naked recombinant DNA or plasmids. Transfer of theconstruct may be performed by any of the methods mentioned above whichphysically or chemically permeabilize the cell membrane. This isparticularly applicable for transfer in vitro but it may be applied toin vivo use as well. Dubensky et al. (1984) successfully injectedpolyomavirus DNA in the form of calcium phosphate precipitates intoliver and spleen of adult and newborn mice demonstrating active viralreplication and acute infection. Benvenisty and Neshif (1986) alsodemonstrated that direct intraperitoneal injection of calciumphosphate-precipitated plasmids results in expression of the transfectedgenes. It is envisioned that DNA encoding a gene of interest may also betransferred in a similar manner in vivo and express the gene product.

In still another embodiment of the disclosure for transferring a nakedDNA expression construct into cells may involve particle bombardment.This method depends on the ability to accelerate DNA-coatedmicroprojectiles to a high velocity allowing them to pierce cellmembranes and enter cells without killing them (Klein et al., 1987).Several devices for accelerating small particles have been developed.One such device relies on a high voltage discharge to generate anelectrical current, which in turn provides the motive force (Yang etal., 1990). The microprojectiles used have consisted of biologicallyinert substances such as tungsten or gold beads.

Selected organs including the liver, skin, and muscle tissue of rats andmice have been bombarded in vivo (Yang et al., 1990; Zelenin et al.,1991). This may require surgical exposure of the tissue or cells, toeliminate any intervening tissue between the gun and the target organ,i.e., ex vivo treatment. Again, DNA encoding a particular gene may bedelivered via this method and still be incorporated by the presentdisclosure.

In a further embodiment of the disclosure, the expression construct maybe entrapped in a liposome. Liposomes are vesicular structurescharacterized by a phospholipid bilayer membrane and an inner aqueousmedium. Multilamellar liposomes have multiple lipid layers separated byaqueous medium. They form spontaneously when phospholipids are suspendedin an excess of aqueous solution. The lipid components undergoself-rearrangement before the formation of closed structures and entrapwater and dissolved solutes between the lipid bilayers (Ghosh andBachhawat, 1991). Also contemplated are lipofectamine-DNA complexes.

Liposome-mediated nucleic acid delivery and expression of foreign DNA invitro has been very successful. Wong et al., (1980) demonstrated thefeasibility of liposome-mediated delivery and expression of foreign DNAin cultured chick embryo, HeLa and hepatoma cells. Nicolau et al.,(1987) accomplished successful liposome-mediated gene transfer in ratsafter intravenous injection. A reagent known as Lipofectamine 2000™ iswidely used and commercially available.

In certain embodiments of the disclosure, the liposome may be complexedwith a hemagglutinating virus (HVJ). This has been shown to facilitatefusion with the cell membrane and promote cell entry ofliposome-encapsulated DNA (Kaneda et al., 1989). In other embodiments,the liposome may be complexed or employed in conjunction with nuclearnon-histone chromosomal proteins (HMG-1) (Kato et al., 1991). In yetfurther embodiments, the liposome may be complexed or employed inconjunction with both HVJ and HMG-1. In that such expression constructshave been successfully employed in transfer and expression of nucleicacid in vitro and in vivo, then they are applicable for the presentdisclosure. Where a bacterial promoter is employed in the DNA construct,it also will be desirable to include within the liposome an appropriatebacterial polymerase.

Other expression constructs which can be employed to deliver a nucleicacid encoding a particular gene into cells are receptor-mediateddelivery vehicles. These take advantage of the selective uptake ofmacromolecules by receptor-mediated endocytosis in almost all eukaryoticcells. Because of the cell type-specific distribution of variousreceptors, the delivery can be highly specific (Wu and Wu, 1993).

Receptor-mediated gene targeting vehicles generally consist of twocomponents: a cell receptor-specific ligand and a DNA-binding agent.Several ligands have been used for receptor-mediated gene transfer. Themost extensively characterized ligands are asialoorosomucoid (ASOR) (Wuand Wu, 1987) and transferrin (Wagner et al., 1990). Recently, asynthetic neoglycoprotein, which recognizes the same receptor as ASOR,has been used as a gene delivery vehicle (Ferkol et al., 1993; Peraleset al., 1994) and epidermal growth factor (EGF) has also been used todeliver genes to squamous carcinoma cells (Myers, EPO 0273085).

D. Antagonists

In another embodiment, use of antagonist to treat pathologic boneformation is also contemplated. The following discussion of CLEC11aantagonists is provided.

1. Antibodies

Antibodies to CLEC11a may be produced by standard methods as are wellknown in the art (see, e.g., Antibodies: A Laboratory Manual, ColdSpring Harbor Laboratory, 1988; U.S. Pat. No. 4,196,265). The methodsfor generating monoclonal antibodies (MAbs) generally begin along thesame lines as those for preparing polyclonal antibodies. The first stepfor both these methods is immunization of an appropriate host oridentification of subjects who are immune due to prior naturalinfection. As is well known in the art, a given composition forimmunization may vary in its immunogenicity. It is often necessarytherefore to boost the host immune system, as may be achieved bycoupling a peptide or polypeptide immunogen to a carrier. Exemplary andpreferred carriers are keyhole limpet hemocyanin (KLH) and bovine serumalbumin (BSA). Other albumins such as ovalbumin, mouse serum albumin orrabbit serum albumin can also be used as carriers. Means for conjugatinga polypeptide to a carrier protein are well known in the art and includeglutaraldehyde, m-maleimidobencoyl-N-hydroxysuccinimide ester,carbodiimide and bis-biazotized benzidine. As also is well known in theart, the immunogenicity of a particular immunogen composition can beenhanced by the use of non-specific stimulators of the immune response,known as adjuvants. Exemplary and preferred adjuvants include completeFreund's adjuvant (a non-specific stimulator of the immune responsecontaining killed Mycobacterium tuberculosis), incomplete Freund'sadjuvants and aluminum hydroxide adjuvant.

The amount of immunogen composition used in the production of polyclonalantibodies varies upon the nature of the immunogen as well as the animalused for immunization. A variety of routes can be used to administer theimmunogen (subcutaneous, intramuscular, intradermal, intravenous andintraperitoneal). The production of polyclonal antibodies may bemonitored by sampling blood of the immunized animal at various pointsfollowing immunization. A second, booster injection, also may be given.The process of boosting and titering is repeated until a suitable titeris achieved. When a desired level of immunogenicity is obtained, theimmunized animal can be bled and the serum isolated and stored, and/orthe animal can be used to generate MAbs.

MAbs produced by either means may be further purified, if desired, usingfiltration, centrifugation and various chromatographic methods such asFPLC or affinity chromatography. Fragments of the monoclonal antibodiesof the disclosure can be obtained from the purified monoclonalantibodies by methods which include digestion with enzymes, such aspepsin or papain, and/or by cleavage of disulfide bonds by chemicalreduction. Alternatively, monoclonal antibody fragments encompassed bythe present disclosure can be synthesized using an automated peptidesynthesizer.

It also is contemplated that a molecular cloning approach may be used togenerate monoclonals. For this, RNA can be isolated from the hybridomaline and the antibody genes obtained by RT-PCR and cloned into animmunoglobulin expression vector. Alternatively, combinatorialimmunoglobulin phagemid libraries are prepared from RNA isolated fromthe cell lines and phagemids expressing appropriate antibodies areselected by panning using viral antigens. The advantages of thisapproach over conventional hybridoma techniques are that approximately10⁴ times as many antibodies can be produced and screened in a singleround, and that new specificities are generated by H and L chaincombination which further increases the chance of finding appropriateantibodies.

Other U.S. patents, each incorporated herein by reference, that teachthe production of antibodies useful in the present disclosure includeU.S. Pat. No. 5,565,332, which describes the production of chimericantibodies using a combinatorial approach; U.S. Pat. No. 4,816,567 whichdescribes recombinant immunoglobulin preparations; and U.S. Pat. No.4,867,973 which describes antibody-therapeutic agent conjugates.

In various embodiments, one may choose to engineer sequences of theidentified antibodies for a variety of reasons, such as improvedexpression, improved cross-reactivity, diminished off-target binding orabrogation of one or more natural effector functions, such as activationof complement or recruitment of immune cells (e.g., T cells). Inparticular, IgM antibodies may be converted to IgG antibodies. Thefollowing is a general discussion of relevant techniques for antibodyengineering.

Hybridomas may be cultured, then cells lysed, and total RNA extracted.Random hexamers may be used with RT to generate cDNA copies of RNA, andthen PCR performed using a multiplex mixture of PCR primers expected toamplify all human variable gene sequences. PCR product can be clonedinto pGEM-T Easy vector, then sequenced by automated DNA sequencingusing standard vector primers. Assay of binding and neutralization maybe performed using antibodies collected from hybridoma supernatants andpurified by FPLC, using Protein G columns. Recombinant full length IgGantibodies can be generated by subcloning heavy and light chain Fv DNAsfrom the cloning vector into a Lonza pConIgG1 or pConK2 plasmid vector,transfected into 293 Freestyle cells or Lonza CHO cells, and collectedand purified from the CHO cell supernatant.

The rapid availability of antibody produced in the same host cell andcell culture process as the final cGMP manufacturing process has thepotential to reduce the duration of process development programs. Lonzahas developed a generic method using pooled transfectants grown in CDACFmedium, for the rapid production of small quantities (up to 50 g) ofantibodies in CHO cells. Although slightly slower than a true transientsystem, the advantages include a higher product concentration and use ofthe same host and process as the production cell line. Example of growthand productivity of GS-CHO pools, expressing a model antibody, in adisposable bioreactor: in a disposable bag bioreactor culture (5 Lworking volume) operated in fed-batch mode, a harvest antibodyconcentration of 2 g/L was achieved within 9 weeks of transfection.

pCon Vectors™ are an easy way to re-express whole antibodies. Theconstant region vectors are a set of vectors offering a range ofimmunoglobulin constant region vectors cloned into the pEE vectors.These vectors offer easy construction of full length antibodies withhuman constant regions and the convenience of the GS System™.

Antibody molecules will comprise fragments (such as F(ab′), F(ab′)₂)that are produced, for example, by the proteolytic cleavage of the mAbs,or single-chain immunoglobulins producible, for example, via recombinantmeans. Such antibody derivatives are monovalent. In one embodiment, suchfragments can be combined with one another, or with other antibodyfragments or receptor ligands to form “chimeric” binding molecules.Significantly, such chimeric molecules may contain substituents capableof binding to different epitopes of the same molecule.

It may be desirable to “humanize” antibodies produced in non-human hostsin order to attenuate any immune reaction when used in human therapy.Such humanized antibodies may be studied in an in vitro or an in vivocontext. Humanized antibodies may be produced, for example by replacingan immunogenic portion of an antibody with a corresponding, butnon-immunogenic portion (i.e., chimeric antibodies). PCT ApplicationPCT/US86/02269; EP Application 184,187; EP Application 171,496; EPApplication 173,494; PCT Application WO 86/01533; EP Application125,023; Sun et al. (1987); Wood et al. (1985); and Shaw et al. (1988);all of which references are incorporated herein by reference. Generalreviews of “humanized” chimeric antibodies are provided by Morrison(1985); also incorporated herein by reference. “Humanized” antibodiescan alternatively be produced by CDR or CEA substitution. Jones et al.(1986); Verhoeyen et al. (1988); Beidler et al. (1988); all of which areincorporated herein by reference.

Modified antibodies may be made by any technique known to those of skillin the art, including expression through standard molecular biologicaltechniques, or the chemical synthesis of polypeptides. Methods forrecombinant expression are addressed elsewhere in this document.

A Single Chain Variable Fragment (scFv) is a fusion of the variableregions of the heavy and light chains of immunoglobulins, linkedtogether with a short (usually serine, glycine) linker. This chimericmolecule, also known as a single domain antibody, retains thespecificity of the original immunoglobulin, despite removal of theconstant regions and the introduction of a linker peptide. Thismodification usually leaves the specificity unaltered. These moleculeswere created historically to facilitate phage display where it is highlyconvenient to express the antigen binding domain as a single peptide.Alternatively, scFv can be created directly from subcloned heavy andlight chains derived from a hybridoma. Single domain or single chainvariable fragments lack the constant Fc region found in completeantibody molecules, and thus, the common binding sites (e.g., proteinA/G) used to purify antibodies (single chain antibodies include the Fcregion). These fragments can often be purified/immobilized using ProteinL since Protein L interacts with the variable region of kappa lightchains.

Flexible linkers generally are comprised of helix- and turn-promotingamino acid residues such as alaine, serine and glycine. However, otherresidues can function as well. Tang et al. (1996) used phage display asa means of rapidly selecting tailored linkers for single-chainantibodies (scFvs) from protein linker libraries. A random linkerlibrary was constructed in which the genes for the heavy and light chainvariable domains were linked by a segment encoding an 18-amino acidpolypeptide of variable composition. The scFv repertoire (approx. 5×10⁶different members) was displayed on filamentous phage and subjected toaffinity selection with hapten. The population of selected variantsexhibited significant increases in binding activity but retainedconsiderable sequence diversity. Screening 1054 individual variantssubsequently yielded a catalytically active scFv that was producedefficiently in soluble form. Sequence analysis revealed a conservedproline in the linker two residues after the V_(H) C terminus and anabundance of arginines and prolines at other positions as the onlycommon features of the selected tethers.

The recombinant antibodies of the present disclosure may also involvesequences or moieties that permit dimerization or multimerization of thereceptors. Such sequences include those derived from IgA, which permitformation of multimers in conjunction with the J-chain. Anothermultimerization domain is the Gal4 dimerization domain. In otherembodiments, the chains may be modified with agents such asbiotin/avidin, which permit the combination of two antibodies.

Artificial T cell receptors (also known as chimeric T cell receptors,chimeric immunoreceptors, chimeric antigen receptors (CARs)) areengineered receptors, which graft an arbitrary specificity onto animmune effector cell. Typically, these receptors are used to graft thespecificity of a monoclonal antibody onto a T cell, with transfer oftheir coding sequence facilitated by retroviral vectors. In this way, alarge number of cancer-specific T cells can be generated for adoptivecell transfer. Phase I clinical studies of this approach show efficacy.

The most common form of these molecules are fusions of single-chainvariable fragments (scFv) derived from monoclonal antibodies, fused toCD3-zeta transmembrane and endodomain. Such molecules result in thetransmission of a zeta signal in response to recognition by the scFv ofits target. An example of such a construct is 14g2a-Zeta, which is afusion of a scFv derived from hybridoma 14g2a (which recognizesdisialoganglioside GD2). When T cells express this molecule (usuallyachieved by oncoretroviral vector transduction), they recognize and killtarget cells that express GD2 (e.g., neuroblastoma cells). To targetmalignant B cells, investigators have redirected the specificity of Tcells using a chimeric immunoreceptor specific for the B-lineagemolecule, CD19.

The variable portions of an immunoglobulin heavy and light chain arefused by a flexible linker to form a scFv. This scFv is preceded by asignal peptide to direct the nascent protein to the endoplasmicreticulum and subsequent surface expression (this is cleaved). Aflexible spacer allows to the scFv to orient in different directions toenable antigen binding. The transmembrane domain is a typicalhydrophobic alpha helix usually derived from the original molecule ofthe signalling endodomain which protrudes into the cell and transmitsthe desired signal.

Type I proteins are in fact two protein domains linked by atransmembrane alpha helix in between. The cell membrane lipid bilayer,through which the transmembrane domain passes, acts to isolate theinside portion (endodomain) from the external portion (ectodomain). Itis not so surprising that attaching an ectodomain from one protein to anendodomain of another protein results in a molecule that combines therecognition of the former to the signal of the latter.

2. Inhibitory Nucleic Acids

Antisense methodology takes advantage of the fact that nucleic acidstend to pair with “complementary” sequences. By complementary, it ismeant that polynucleotides are those which are capable of base-pairingaccording to the standard Watson-Crick complementarity rules. That is,the larger purines will base pair with the smaller pyrimidines to formcombinations of guanine paired with cytosine (G:C) and adenine pairedwith either thymine (A:T) in the case of DNA, or adenine paired withuracil (A:U) in the case of RNA. Inclusion of less common bases such asinosine, 5-methylcytosine, 6-methyladenine, hypoxanthine and others inhybridizing sequences does not interfere with pairing.

Targeting double-stranded (ds) DNA with polynucleotides leads totriple-helix formation; targeting RNA will lead to double-helixformation. Antisense polynucleotides, when introduced into a targetcell, specifically bind to their target polynucleotide and interferewith transcription, RNA processing, transport, translation and/orstability. Antisense RNA constructs, or DNA encoding such antisenseRNA's, may be employed to inhibit gene transcription or translation orboth within a host cell, either in vitro or in vivo, such as within ahost animal, including a human subject.

Antisense constructs may be designed to bind to the promoter and othercontrol regions, exons, introns or even exon-intron boundaries of agene. It is contemplated that the most effective antisense constructswill include regions complementary to intron/exon splice junctions.Thus, it is proposed that a preferred embodiment includes an antisenseconstruct with complementarity to regions within 50-200 bases of anintron-exon splice junction. It has been observed that some exonsequences can be included in the construct without seriously affectingthe target selectivity thereof. The amount of exonic material includedwill vary depending on the particular exon and intron sequences used.One can readily test whether too much exon DNA is included simply bytesting the constructs in vitro to determine whether normal cellularfunction is affected or whether the expression of related genes havingcomplementary sequences is affected.

As stated above, “complementary” or “antisense” means polynucleotidesequences that are substantially complementary over their entire lengthand have very few base mismatches. For example, sequences of fifteenbases in length may be termed complementary when they have complementarynucleotides at thirteen or fourteen positions. Naturally, sequenceswhich are completely complementary will be sequences which are entirelycomplementary throughout their entire length and have no basemismatches. Other sequences with lower degrees of homology also arecontemplated. For example, an antisense construct which has limitedregions of high homology, but also contains a non-homologous region(e.g., ribozyme; see below) could be designed. These molecules, thoughhaving less than 50% homology, would bind to target sequences underappropriate conditions.

It may be advantageous to combine portions of genomic DNA with cDNA orsynthetic sequences to generate specific constructs. For example, wherean intron is desired in the ultimate construct, a genomic clone willneed to be used. The cDNA or a synthesized polynucleotide may providemore convenient restriction sites for the remaining portion of theconstruct and, therefore, would be used for the rest of the sequence.

Another general class of nucleic acid based inhibitors is ribozymes.Although proteins traditionally have been used for catalysis of nucleicacids, another class of macromolecules has emerged as useful in thisendeavor. Ribozymes are RNA-protein complexes that cleave nucleic acidsin a site-specific fashion. Ribozymes have specific catalytic domainsthat possess endonuclease activity (Kim and Cook, 1987; Gerlach et al.,1987; Forster and Symons, 1987). For example, a large number ofribozymes accelerate phosphoester transfer reactions with a high degreeof specificity, often cleaving only one of several phosphoesters in anoligonucleotide substrate (Cook et al., 1981; Michel and Westhof, 1990;Reinhold-Hurek and Shub, 1992). This specificity has been attributed tothe requirement that the substrate bind via specific base-pairinginteractions to the internal guide sequence (“IGS”) of the ribozymeprior to chemical reaction.

Ribozyme catalysis has primarily been observed as part ofsequence-specific cleavage/ligation reactions involving nucleic acids(Joyce, 1989; Cook et al., 1981). For example, U.S. Pat. No. 5,354,855reports that certain ribozymes can act as endonucleases with a sequencespecificity greater than that of known ribonucleases and approachingthat of the DNA restriction enzymes. Thus, sequence-specificribozyme-mediated inhibition of gene expression may be particularlysuited to therapeutic applications (Scanlon et al., 1991; Sarver et al.,1990). It has also been shown that ribozymes can elicit genetic changesin some cells lines to which they were applied; the altered genesincluded the oncogenes H-ras, c-fos and genes of HIV. Most of this workinvolved the modification of a target mRNA, based on a specific mutantcodon that was cleaved by a specific ribozyme.

RNA interference (also referred to as “RNA-mediated interference” orRNAi) is another mechanism by which protein expression can be reduced oreliminated. Double-stranded RNA (dsRNA) has been observed to mediate thereduction, which is a multi-step process. dsRNA activatespost-transcriptional gene expression surveillance mechanisms that appearto function to defend cells from virus infection and transposon activity(Fire et al., 1998; Grishok et al., 2000; Ketting et al., 1999; Lin etal., 1999; Montgomery et al., 1998; Sharp et al., 2000; Tabara et al.,1999). Activation of these mechanisms targets mature,dsRNA-complementary mRNA for destruction. RNAi offers major experimentaladvantages for study of gene function. These advantages include a veryhigh specificity, ease of movement across cell membranes, and prolongeddown-regulation of the targeted gene (Fire et al., 1998; Grishok et al.,2000; Ketting et al., 1999; Lin et al., 1999; Montgomery et al., 1998;Sharp, 1999; Sharp et al., 2000; Tabara et al., 1999). Moreover, dsRNAhas been shown to silence genes in a wide range of systems, includingplants, protozoans, fungi, C. elegans, Trypanasoma, Drosophila, andmammals (Grishok et al., 2000; Sharp, 1999; Sharp et al., 2000; Elbashiret al., 2001). It is generally accepted that RNAi actspost-transcriptionally, targeting RNA transcripts for degradation, andpossibly by inhibiting translation. It appears that both nuclear andcytoplasmic RNA can be targeted (Bosher et al., 2000).

siRNAs must be designed so that they are specific and effective insuppressing the expression of the genes of interest. Methods ofselecting the target sequences, i.e. those sequences present in the geneor genes of interest to which the siRNAs will guide the degradativemachinery, are directed to avoiding sequences that may interfere withthe siRNA's guide function while including sequences that are specificto the gene or genes. Typically, siRNA target sequences of about 21 to23 nucleotides in length are most effective. This length reflects thelengths of digestion products resulting from the processing of muchlonger RNAs as described above (Montgomery et al., 1998). Of particularinterest are those siRNAs that span an exon-intron junction.

The making of siRNAs has been mainly through direct chemical synthesis;through processing of longer, double stranded RNAs through exposure toDrosophila embryo lysates; or through an in vitro system derived from S2cells. Use of cell lysates or in vitro processing may further involvethe subsequent isolation of the short, 21-23 nucleotide siRNAs from thelysate, etc., making the process somewhat cumbersome and expensive.Chemical synthesis proceeds by making two single-stranded RNA-oligomersfollowed by the annealing of the two single-stranded oligomers into adouble stranded RNA. Methods of chemical synthesis are diverse.Non-limiting examples are provided in U.S. Pat. Nos. 5,889,136,4,415,732, and 4,458,066, expressly incorporated herein by reference,and in Wincott et al. (1995).

Several further modifications to siRNA sequences have been suggested inorder to alter their stability or improve their effectiveness. It issuggested that synthetic complementary 21-mer RNAs having di-nucleotideoverhangs (i.e., 19 complementary nucleotides+3′ non-complementarydimers) may provide the greatest level of suppression. These protocolsprimarily use a sequence of two (2′-deoxy) thymidine nucleotides as thedi-nucleotide overhangs. These dinucleotide overhangs are often writtenas dTdT to distinguish them from the typical nucleotides incorporatedinto RNA. The literature has indicated that the use of dT overhangs isprimarily motivated by the need to reduce the cost of the chemicallysynthesized RNAs. It is also suggested that the dTdT overhangs might bemore stable than UU overhangs, though the data available shows only aslight (<20%) improvement of the dTdT overhang compared to an siRNA witha UU overhang.

Chemically synthesized siRNAs are found to work optimally when they arein cell culture at concentrations of 25-100 nM. This had beendemonstrated by Elbashir et al. (2001) wherein concentrations of about100 nM achieved effective suppression of expression in mammalian cells.siRNAs have been most effective in mammalian cell culture at about 100nM. In several instances, however, lower concentrations of chemicallysynthesized siRNA have been used (Caplen et al., 2000; Elbashir et al.,2001).

WO 99/32619 and WO 01/68836 suggest that RNA for use in siRNA may bechemically or enzymatically synthesized. Both of these texts areincorporated herein in their entirety by reference. The enzymaticsynthesis contemplated in these references is by a cellular RNApolymerase or a bacteriophage RNA polymerase (e.g., T3, T7, SP6) via theuse and production of an expression construct as is known in the art.See U.S. Pat. No. 5,795,715. The contemplated constructs providetemplates that produce RNAs that contain nucleotide sequences identicalto a portion of the target gene. The length of identical sequencesprovided by these references is at least 25 bases, and may be as many as400 or more bases in length. An important aspect of this reference isthat the authors contemplate digesting longer dsRNAs to 21-25 merlengths with the endogenous nuclease complex that converts long dsRNAsto siRNAs in vivo. They do not describe or present data for synthesizingand using in vitro transcribed 21-25 mer dsRNAs. No distinction is madebetween the expected properties of chemical or enzymatically synthesizeddsRNA in its use in RNA interference.

Similarly, WO 00/44914, incorporated herein by reference, suggests thatsingle strands of RNA can be produced enzymatically or by partial/totalorganic synthesis. Preferably, single stranded RNA is enzymaticallysynthesized from the PCR™ products of a DNA template, preferably acloned cDNA template and the RNA product is a complete transcript of thecDNA, which may comprise hundreds of nucleotides. WO 01/36646,incorporated herein by reference, places no limitation upon the mannerin which the siRNA is synthesized, providing that the RNA may besynthesized in vitro or in vivo, using manual and/or automatedprocedures. This reference also provides that in vitro synthesis may bechemical or enzymatic, for example using cloned RNA polymerase (e.g.,T3, T7, SP6) for transcription of the endogenous DNA (or cDNA) template,or a mixture of both. Again, no distinction in the desirable propertiesfor use in RNA interference is made between chemically or enzymaticallysynthesized siRNA.

U.S. Pat. No. 5,795,715 reports the simultaneous transcription of twocomplementary DNA sequence strands in a single reaction mixture, whereinthe two transcripts are immediately hybridized. The templates used arepreferably of between 40 and 100 base pairs, and which is equipped ateach end with a promoter sequence. The templates can be attached to asolid surface. After transcription with RNA polymerase, the resultingdsRNA fragments may be used for detecting and/or assaying nucleic acidtarget sequences.

In a specific embodiment, the inventors propose to inhibit CLEC11aexpression in adult tissues in vitro using siRNA or shRNA in alentiviral vector. A GFP marker can be utilized to determine that cellstook up the vector, and thus permit checking for appropriate inhibitionof CLEC11a production. The use of an inducible promoter (discussedbelow) that allow induction of the siRNA or shRNA only under specificgrowth conditions permit reversible inhibition of CLEC11a. Self-deletingvectors may also be used.

II. BONE STRUCTURE AND PHYSIOLOGY

Bone is a living, growing tissue. It is porous and mineralized, and madeup of cells, vessels, organic matrix and inorganic hydroxyapatitecrystals. The human skeleton is actually made up of 2 types of bones:the cortical bone and the trabecular bone. Cortical bone representsnearly 80% of the skeletal mass. Cortical bone has a slow turnover rateand a high resistance to bending and torsion. It provides strength wherebending would be undesirable as in the middle of long bones. Trabecularbone only represents 20% of the skeletal mass, but 80% of the bonesurface. It is less dense, more elastic and has a higher turnover ratethan cortical bone.

A. Bone Forming Cells

Osteoprogenitors.

Human bone precursor cells are characterized as small-sized cells thatexpress low amounts of bone proteins (osteocalcin, osteonectin, andalkaline phosphatase) and have a low degree of internal complexity (Longet al., 1995). When stimulated to differentiate, these preosteoblastcells become osteoblast in their appearance, size, antigenic expression,and internal structure. Although these cells are normally present atvery low frequencies in bone marrow, a process for isolating these cellshas been described (U.S. Pat. No. 5,972,703).

A number of studies indicate that bone marrow derived cells haveosteogenic potential. The majority of these investigations point tomesenchymal stem cells (MSC) as undergoing differentiation intoosteoblasts when cultured in the presence of bone-active cytokines.Mesenchymal stem cells are a pluripotent population capable ofgenerating multiple stromal cell lineages. MSC, as currently used, are aheterogeneous population of cells isolated by plastic adherence, andpropagated by low-density passage. Nonetheless, a recent publicationindicates the clonal nature of cell fate outcomes in MSC indicating thata single MSC cell can give rise to two or three mesenchymal lineages oneof which is usually bone cells. These studies are consistent withearlier reports that demonstrated the osteogenic potential of bonemarrow stromal cells, in particular the so-called CFU-f from both miceand human.

Single-cell isolation of human MSC generated clones that express thesame surface phenotype as unfractionated MSC. Interestingly, of the 6MSC clones evaluated, 2 retained osteogenic, chrondrogenic andadipogenic potential; others were bipotent (either osteo-pluschondrogenic potential, or osteo-adipocytic potential) or wereuni-lineage (chondrocyte). This suggests that MSC themselves areheterogeneous in nature (although culture conditions also may have ledto loss of lineage potential). To date, the self-renewal capacity of MSCremains in question. Nonetheless, these in vitro studies and other invivo studies show that MSC can commit to the bone cell lineage anddevelop to the state of matrix mineralization in vitro, or boneformation in vivo.

Preosteoblasts.

Preosteoblasts are intermediate between osteoprogenitor cells andosteoblasts. They show increasing expression of bone phenotypic markerssuch as alkaline phosphatase. They have a more limited proliferativecapacity, but nonetheless continue to divide and produce morepreosteoblasts or osteoblasts.

Osteoblasts.

An osteoblast is a mononucleate cell that is responsible for boneformation. Osteoblasts produce osteoid, which is composed mainly of TypeI collagen. Osteoblasts are also responsible for mineralization of theosteoid matrix. Bone is a dynamic tissue that is constantly beingreshaped by osteoblasts, which build bone, and osteoclasts, which resorbbone. Osteoblast cells tend to decrease in number and activity asindividuals become elderly, thus decreasing the natural renovation ofthe bone tissue.

Osteoblasts arise from osteoprogenitor cells located in the periosteumand the bone marrow. Osteoprogenitors are immature progenitor cells thatexpress the master regulatory transcription factor Cbfa1/Runx2.Osteoprogenitors are induced to differentiate under the influence ofgrowth factors, in particular the bone morphogenetic proteins (BMPs).Aside from BMPs, other growth factors including fibroblast growth factor(FGF), platelet-derived growth factor (PDGF), transforming growth factorbeta (TGF-beta) may promote the division of osteoprogenitors andpotentially increase osteogenesis. Once osteoprogenitors start todifferentiate into osteoblasts, they begin to express a range of geneticmarkers including Osterix, Col1, ALP, osteocalcin, osteopontin, andosteonectin. Although the term osteoblast implies an immature cell type,osteoblasts are in fact the mature bone cells entirely responsible forgenerating bone tissue in animals and humans.

Osteoclasts.

An osteoclast is a type of bone cell that removes bone tissue byremoving its mineralized matrix. This process is known as boneresorption. Osteoclasts and osteoblasts are instrumental in controllingthe amount of bone tissue: osteoblasts form bone, osteoclasts resorbbone. Osteoclasts are formed by the fusion of cells of themonocyte-macrophage cell lineage. Osteoclasts are characterized by highexpression of tartrate resistant acid phosphatase (TRAP) and cathepsinK.

Osteoclast formation requires the presence of RANK ligand (receptoractivator of nuclear factor κβ) and M-CSF (Macrophage colony-stimulatingfactor). These membrane bound proteins are produced by neighbouringstromal cells and osteoblasts; thus requiring direct contact betweenthese cells and osteoclast precursors. M-CSF acts through its receptoron the osteoclast, c-fms (colony stimulating factor 1 receptor), atransmembrane tyrosine kinase-receptor, leading to secondary messengeractivation of tyrosine kinase Src. Both of these molecules are necessaryfor osteoclastogenesis and are widely involved in the differentiation ofmonocyte/macrophage derived cells. RANKL is a member of the tumornecrosis family (TNF), and is essential in osteoclastogenesis. RANKLknockout mice exhibit a phenotype of osteopetrosis and defects of tootheruption, along with an absence or deficiency of osteoclasts. RANKLactivates NF-κβ and NFATc1 (nuclear factor of activated t cells,cytoplasmic, calcineurin-dependent 1) through RANK. NF-κβ activation isstimulated almost immediately after RANKL-RANK interaction occurs, andis not upregulated. NFATc1 stimulation, however, begins about 24-48hours after binding occurs and its expression has been shown to be RANKLdependent. Osteoclast differentiation is inhibited by osteoprotegerin(OPG), which binds to RANKL thereby preventing interaction with RANK.

B. Bone Formation

The formation of bone during the fetal stage of development occurs bytwo processes: intramembranous ossification and endochondralossification. Intramembranous ossification mainly occurs duringformation of the flat bones of the skull; the bone is formed frommesenchyme tissue. The steps in intramembranous ossification aredevelopment of ossification center, calcification, formation oftrabeculae and development of periosteum. Endochondral ossification, onthe other hand, occurs in long bones, such as limbs; the bone is formedaround a cartilage template. The steps in endochondral ossification aredevelopment of cartilage model, growth of cartilage model, developmentof the primary ossification center and development of the secondaryossification center.

Endochondral ossification begins with points in the cartilage called“primary ossification centers.” They mostly appear during fetaldevelopment, though a few short bones begin their primary ossificationafter birth. They are responsible for the formation of the diaphyses oflong bones, short bones and certain parts of irregular bones. Secondaryossification occurs after birth, and forms the epiphyses of long bonesand the extremities of irregular and flat bones. The diaphysis and bothepiphyses of a long bone are separated by a growing zone of cartilage(the epiphyseal plate). When the child reaches skeletal maturity (18 to25 years of age), all of the cartilage is replaced by bone, fusing thediaphysis and both epiphyses together (epiphyseal closure).

Remodeling or bone turnover is the process of resorption followed byreplacement of bone with little change in shape and occurs throughout aperson's life. Osteoblasts and osteoclasts, coupled together viaparacrine cell signalling, are referred to as bone remodeling units. Thepurpose of remodeling is to regulate calcium homeostasis, repairmicro-damaged bones (from everyday stress) but also to shape andsculpture the skeleton during growth.

The process of bone resorption by the osteoclasts releases storedcalcium into the systemic circulation and is an important process inregulating calcium balance. As bone formation actively fixes circulatingcalcium in its mineral form, removing it from the bloodstream,resorption actively unfixes it thereby increasing circulating calciumlevels. These processes occur in tandem at site-specific locations.

Repeated stress, such as weight-bearing exercise or bone healing,results in the bone thickening at the points of maximum stress (Wolff slaw). It has been hypothesized that this is a result of bone'spiezoelectric properties, which cause bone to generate small electricalpotentials under stress.

III. TREATMENTS

A. Bone Deficit Diseases and Conditions

There are a plethora of conditions which are characterized by the needto enhance bone formation or to inhibit bone resorption and thus wouldbenefit from the use of CLEC11a and agonists thereof in promoting boneformation and/or bone repair. Perhaps the most obvious is the case ofbone fractures, where it would be desirable to stimulate bone growth andto hasten and complete bone repair. Agents that enhance bone formationwould also be useful in facial reconstruction procedures. Other bonedeficit conditions include bone segmental defects, periodontal disease,metastatic bone disease, osteolytic bone disease and conditions whereconnective tissue repair would be beneficial, such as healing orregeneration of cartilage defects or injury. Also of great significanceis the chronic condition of osteoporosis, including age-relatedosteoporosis and osteoporosis associated with post-menopausal hormonestatus. Other conditions characterized by the need for bone growthinclude primary and secondary hyperparathyroidism, disuse osteoporosis,diabetes-related osteoporosis, and glucocorticoid-related osteoporosis.Several other conditions, such as, for example, vitamin D deficiency,exists.

Spinal Fusion.

Spinal fusion, also called spondylodesis or spondylosyndesis, is aneurosurgical or orthopedic surgical technique that joins two or morevertebrae. Surgeons use supplementary bone tissue—either from thepatient (autograft) or a donor (allograft)—or artificial bonesubstitutes in conjunction with the body's natural bone growth(osteoblastic) processes to fuse two or more adjoining vertebrae. Spinalfusion treats a variety of pathological conditions to eliminate abnormalmotion of the vertebrae that causes pain, neurological deficit, orspinal deformity. Common conditions incorporating spinal fusion in theirsurgical treatment are spinal stenosis, spondylolisthesis, cervicaldiscopathy, spinal fractures, scoliosis, and kyphosis.

Fracture.

The first example is the otherwise healthy individual who suffers afracture. Often, clinical bone fracture is treated by casting toalleviate pain and allow natural repair mechanisms to repair the wound.There has been progress in the treatment of fracture in recent times,however, even without considering the various complications that mayarise in treating fractured bones, any new procedures to increase bonehealing in normal circumstances would represent a great advance.

Periodontal Disease.

Progressive periodontal disease leads to tooth loss through destructionof the tooth's attachment to the surrounding bone. Approximately 5-20%of the U.S. population (15-60 million individuals) suffers from severegeneralized periodontal disease, and there are 2 million relatedsurgical procedures. Moreover, if the disease is defined as theidentification of at least one site of clinical attachment loss, thenapproximately 80% of all adults are affected, and 90% of those aged 55to 64 years. If untreated, approximately 88% of affected individualsshow moderate to rapid progression of the disease′ which shows a strongcorrelation with age. The major current treatment for periodontaldisease is regenerative therapy consisting of replacement of lostperiodontal tissues. The lost bone is usually treated with anindividual's own bone and bone marrow, due to their high osteogenicpotential. Bone allografts (between individuals) can also be performedusing stored human bone. Although current periodontal cost analyses arehard to obtain, the size of the affected population and the current useof bone grafts as a first-order therapy strongly suggest that this arearepresents an attractive target for bone-building therapies.

Osteopenia/Osteoporosis.

The terms osteopenia and osteoporosis refers to a heterogeneous group ofdisorders characterized by decreased bone mass and fractures. Osteopeniais a bone mass that is one or more standard deviations below the meanbone mass for a population; osteoporosis is defined as 2.5 SD or lower.An estimated 20-25 million people are at increased risk for fracturebecause of site-specific bone loss. Risk factors for osteoporosisinclude increasing age, gender (more females), low bone mass, earlymenopause, race (Caucasians in general; asian and hispanic females), lowcalcium intake, reduced physical activity, genetic factors,environmental factors (including cigarette smoking and abuse of alcoholor caffeine), and deficiencies in neuromuscular control that create apropensity to fall.

More than a million fractures in the U.S. each year can be attributed toosteoporosis. In economic terms, the costs (exclusive of lost wages) forosteoporosis therapies are $35 billion worldwide. Demographic trends(i.e., the gradually increasing age of the U.S. population) suggest thatthese costs may increase to $62 billion by the year 2020. Clearly,osteoporosis is a significant health care problem.

Osteoporosis, once thought to be a natural part of aging among women, isno longer considered age or gender-dependent. Osteoporosis is defined asa skeletal disorder characterized by compromised bone strengthpredisposing to an increased risk of fracture. Bone strength reflectsthe integration of two main features: bone density and bone quality.Bone density is expressed as grams of mineral per area or volume and inany given individual is determined by peak bone mass and amount of boneloss. Bone quality refers to architecture, turnover, damage accumulation(e.g., microfractures) and mineralization. A fracture occurs when afailure-inducing force (e.g., trauma) is applied to osteoporotic bone.

Current therapies for osteoporosis patients focus on fractureprevention. This remains an important consideration because of theliterature, which clearly states that significant morbidity andmortality are associated with prolonged bed rest in the elderly,particularly those who have suffered hip fractures. Complications of bedrest include blood clots and pneumonia. These complications arerecognized and measures are usually taken to avoid them, but this ishardly the best approach to therapy. Thus, the osteoporotic patientpopulation would benefit from new therapies designed to increase bonevolume, strengthen bone and speed up the fracture repair process, thusgetting these people on their feet before the complications arise.

Bone Reconstruction/Grafting.

A fourth example is related to bone reconstruction and, specifically,the ability to reconstruct defects in bone tissue that result fromtraumatic injury; as a consequence of cancer or cancer surgery; as aresult of a birth defect; or as a result of aging. There is asignificant need for more frequent orthopedic implants, and cranial andfacial bone are particular targets for this type of reconstructive need.The availability of new implant materials, e.g., titanium, has permittedthe repair of relatively large defects. Titanium implants provideexcellent temporary stability across bony defects and are an excellentmaterial for bone implants or artificial joints such as hip, knee andjoint replacements. However, experience has shown that a lack of viablebone binding to implants the defect can result in exposure of theappliance to infection, structural instability and, ultimately, failureto repair the defect. Thus, a therapeutic agent that stimulates boneformation on or around the implant will facilitate more rapid recovery.

Autologous bone grafts are another possibility, but they have severaldemonstrated disadvantages in that they must be harvested from a donorsite such as iliac crest or rib, they usually provide insufficient boneto completely fill the defect, and the bone that does form is sometimesprone to infection and resorption. Partially purified xenogeneicpreparations are not practical for clinical use because microgramquantities are purified from kilograms of bovine bone, making largescale commercial production both costly and impractical. Allografts anddemineralized bone preparations are therefore often employed, but sufferfrom their devitalized nature in that they only function as scaffoldsfor endogenous bone cell growth.

Microsurgical transfers of free bone grafts with attached soft tissueand blood vessels can close bony defects with an immediate source ofblood supply to the graft. However, these techniques are time consuming,have been shown to produce a great deal of morbidity, and can only beused by specially trained individuals. Furthermore, the bone implant isoften limited in quantity and is not readily contoured. In the mandible,for example, the majority of patients cannot wear dental appliancesusing presently accepted techniques (even after continuity isestablished), and thus gain little improvement in the ability tomasticate.

In connection with bone reconstruction, specific problem areas forimprovement are those concerned with treating large defects, such ascreated by trauma, birth defects, or particularly, following tumorresection; and also the area of artificial joints. The success oforthopaedic implants, interfaces and artificial joints could conceivablybe improved if the surface of the implant, or a functional part of animplant, were to be coated with a bone stimulatory agent. The surface ofimplants could be coated with one or more appropriate materials in orderto promote a more effective interaction with the biological sitesurrounding the implant and, ideally, to promote tissue repair.

Primary Bone Cancer and Metastatic Bone Disease.

Bone cancer occurs infrequently while bone metastases are present in awide range of cancers, including thyroid, kidney, and lung. Metastaticbone cancer is a chronic condition; survival from the time of diagnosisis variable depending on tumor type. In prostate and breast cancer andin multiple myeloma, survival time is measurable in years. For advancedlung cancer, it is measured in months. Cancer symptoms include pain,hypercalcemia, pathologic fracture, and spinal cord or nervecompression. Prognosis of metastatic bone cancer is influenced byprimary tumor site, presence of extra-osseous disease, and the extentand tempo of the bone disease. Bone cancer/metastasis progression isdetermined by imaging tests and measurement of bone specific markers.Recent investigations show a strong correlation between the rate of boneresorption and clinical outcome, both in terms of disease progression ordeath.

Multiple Myeloma.

Multiple myeloma (MM) is a B-lymphocyte malignancy characterized by theaccumulation of malignant clonal plasma cells in the bone marrow. Theclinical manifestations of the disease are due to the replacement ofnormal bone marrow components by abnormal plasma cells, with subsequentoverproduction of a monoclonal immunoglobulin (M protein or Mcomponent), bone destruction, bone pain, anemia, hypercalcemia and renaldysfunction.

As distinct from other cancers that spread to the bone (e.g., breast,lung, thyroid, kidney, prostate), myeloma bone disease (MBD) is not ametastatic disease. Rather, myeloma cells are derived from the B-cellsof the immune system that normally reside in the bone marrow and aretherefore intimately associated with bone. Indeed, the bone marrowmicroenvironment plays an important role in the growth, survival andresistance to chemotherapy of the myeloma cells, which, in turn,regulate the increased bone loss associated with this disorder(world-wide-web at multiplemyeloma.org). Over 90% of myeloma patientshave bone involvement, versus 40-60% of cancer patients who have bonemetastasis, and over 80% have intractable bone pain. Additionally,approximately 30% of myeloma patients have hypercalcemia that is aresult of the increased osteolytic activity associated with thisdisease.

Common problems in myeloma are weakness, confusion and fatigue due tohypercalcemia. Headache, visual changes and retinopathy may be theresult of hyperviscosity of the blood depending on the properties of theparaprotein. Finally, there may be radicular pain, loss of bowel orbladder control (due to involvement of spinal cord leading to cordcompression) or carpal tunnel syndrome and other neuropathies (due toinfiltration of peripheral nerves by amyloid). It may give rise toparaplegia in late presenting cases.

Myeloma Bone Disease.

As discussed above, unlike the osteolysis associated with other bonetumors, the MBD lesions are unique in that they do not heal or repair,despite the patients' having many years of complete remission.Mechanistically, this seems to be related to the inhibition and/or lossof the bone-forming osteoblast during disease progression. Indeed, bonemarker studies and histomorphometry indicate that both thebone-resorbing osteoclast and osteoblast activity are increased, butbalanced early in the disease, whereas overt MBD shows high osteoclastactivity and low osteoblast activity. Thus, MBD is a disorder in whichbone formation and bone loss are uncoupled and would benefit fromtherapies that both stimulate bone formation and retard its loss.

A number of therapeutic approaches have been used in MBD, with theendpoints of treating pain, hypercalcemia, or the reduction of skeletalrelated events (SRE). Many of these may present serious complications.Surgery, such as vertebroplasty or kyphoplasty, that is performed forstability and pain relief has the attendant surgical risks (e.g.,infection) made worse by a compromised immune system and does notreverse existing skeletal defects. Radiation therapy and radioisotopetherapy are both used to prevent/control disease progression and havethe typical risks of irradiation therapies. More recently, drugs such asthe bisphosphonates that inhibit osteoclast activity have become astandard of therapy for MBD, despite the fact that they work poorly inthis disorder. In 9 major double-blind, placebo-controlled trials onbisphosphonates, only 66% of patients showed an effective reduction inpain; 56% showed a reduction in SRE and only 1 of the 9 demonstrated asurvival benefit.

B. Pathologic Bone Formation

Pathologic bone formation is generally categorized into three groupsbased on the initiating stimulus: trauma, tumors, and idiopathic causes.In the trauma category, formation of ectopic bone occurs with major andminor traumatic incidents, surgery, burns, and other causes. For tumors,direct and reactive pathologic bone formation depends on the differentneoplasms capable of ectopic bone formation. Idiopathic causes involvethe formation of pathologic bone following neurologic injury and insystemic ossification disorders. The origin of the bone-forming cells inpathologic bone remains unclear. There is some evidence suggesting thatthese cells may arise from osteogenic stromal elements. Potent boneformation growth-regulating factors likely also participate in theformation of pathologic bone.

C. Combination Treatments

As discussed, the present disclosure provides for the treatment of bonesdisease and bone trauma by stimulating the production of new bonetissue, either locally or systemically. Other agents may be used incombination with CLEC11a or agonists thereof of the present disclosure.More generally, these agents would be provided in a combined amount(along with the CLEC11a or agonists thereof) to produce any of theeffects discussed above. This process may involve contacting the cell orsubject with both agents at the same time. This may be achieved bycontacting the cell with a single composition or pharmacologicalformulation that includes both agents, or by contacting the cell orsubject with two distinct compositions or formulations, at the sametime, wherein one composition includes the intracellular inhibitor andthe other includes the second agent.

Alternatively, one agent may precede or follow the other by intervalsranging from minutes to weeks. In embodiments where the agents areapplied separately to the cell or subject, one would generally ensurethat a significant period of time did not expire between the time ofeach delivery, such that the agents would still be able to exert anadvantageously combined effect on the cell or subject. In suchinstances, it is contemplated that one may contact the cell or subjectwith both modalities within about 12-24 h of each other and, morepreferably, within about 6-12 h of each other. In some situations, itmay be desirable to extend the time period for treatment significantly,however, where several days (2, 3, 4, 5, 6 or 7) to several weeks (1, 2,3, 4, 5, 6, 7 or 8) lapse between the respective administrations.

Various combinations may be employed, the CLEC11a or agonist thereof is“A” and the other agent is “B”:

A/B/A B/A/B B/B/A A/A/B B/A/A A/B/B B/B/B/A B/B/A/B A/A/B/B A/B/A/BA/B/B/A B/B/A/A B/A/B/A B/A/A/B B/B/B/A A/A/A/B B/A/A/A A/B/A/A A/A/B/AA/B/B/B B/A/B/B B/B/A/BAdministration protocols and formulation of such agents will generallyfollow those of standard pharmaceutical drugs, as discussed furtherbelow. Combination agents include bisphosphonates (Didronel®, Fosamax®and Actonel®), SERMs (Evista) or other hormone derivatives, sclerostininhibitors, and Parathyroid Hormone (PTH) or parathyroid related hormoneanalogs.

IV. PHARMACEUTICAL FORMULATIONS AND DELIVERY

A. Compositions and Routes

Pharmaceutical compositions of the present disclosure comprise aneffective amount of CLEC11a or agonists thereof dissolved or dispersedin a pharmaceutically acceptable carrier. The phrases “pharmaceutical orpharmacologically acceptable” refer to molecular entities andcompositions that do not produce an adverse, allergic or other untowardreaction when administered to an animal, such as, for example, a human,as appropriate. The preparation of a pharmaceutical composition thatcontains at least one anti-TGF-beta antibody, and optionally anadditional active ingredient, will be known to those of skill in the artin light of the present disclosure, as exemplified by Remington'sPharmaceutical Sciences, 18th Ed. Mack Printing Company, 1990,incorporated herein by reference. Moreover, for animal (e.g., human)administration, it will be understood that preparations should meetsterility, pyrogenicity, general safety and purity standards as requiredby FDA Office of Biological Standards.

As used herein, “pharmaceutically acceptable carrier” includes any andall solvents, dispersion media, coatings, surfactants, antioxidants,preservatives (e.g., antibacterial agents, antifungal agents), isotonicagents, absorption delaying agents, salts, preservatives, drugs, drugstabilizers, gels, binders, excipients, disintegration agents,lubricants, sweetening agents, flavoring agents, dyes, such likematerials and combinations thereof, as would be known to one of ordinaryskill in the art (see, for example, Remington's Pharmaceutical Sciences,18th Ed. Mack Printing Company, 1990, 1289-1329, incorporated herein byreference). Except insofar as any conventional carrier is incompatiblewith the active ingredient, its use in the pharmaceutical compositionsis contemplated.

The CLEC11a or agonist thereof may be admixed with different types ofcarriers depending on whether it is to be administered orally or byinjection. The present disclosure can be administered buccally,intravenously, intradermally, transdermally, intrathecally,intraarterially, intraperitoneally, topically, intramuscularly,subcutaneously, mucosally, orally, topically, locally, inhalation (e.g.,aerosol inhalation), injection, infusion, continuous infusion, localizedperfusion bathing target cells directly, via a catheter, via a lavage,in cremes, in lipid compositions (e.g., nanoparticles, liposomes), or byother method or any combination of the forgoing as would be known to oneof ordinary skill in the art (see, for example, Remington'sPharmaceutical Sciences, 18th Ed. Mack Printing Company, 1990,incorporated herein by reference). In particular, the CLEC11a or agonistthereof is formulated into a syringeable composition for use inintravenous administration.

The CLEC11a or agonist thereof may be formulated into a composition in afree base, neutral or salt form or ester. It may also besynthesized/formulated in a prodrug form. Pharmaceutically acceptablesalts, include the acid addition salts, e.g., those formed with the freeamino groups of a proteinaceous composition, or which are formed withinorganic acids such as for example, hydrochloric or phosphoric acids,or such organic acids as acetic, oxalic, tartaric, fumaric, or mandelicacid. Salts formed with the free carboxyl groups can also be derivedfrom inorganic bases such as for example, sodium, potassium, ammonium,calcium or ferric hydroxides; or such organic bases as isopropylamine,trimethylamine, histidine or procaine. Upon formulation, solutions willbe administered in a manner compatible with the dosage formulation andin such amount as is therapeutically effective.

Further in accordance with the present disclosure, the composition ofthe present disclosure suitable for administration is provided in apharmaceutically acceptable carrier with or without an inert diluent.The carrier should be assimilable and includes liquid, semi-solid, i.e.,pastes, or solid carriers. Except insofar as any conventional media,agent, diluent or carrier is detrimental to the recipient or to thetherapeutic effectiveness of the composition contained therein, its usein administrable composition for use in practicing the methods of thepresent disclosure is appropriate. Examples of carriers or diluentsinclude fats, oils, water, saline solutions, lipids, liposomes, resins,binders, fillers and the like, or combinations thereof. The compositionmay also comprise various antioxidants to retard oxidation of one ormore component. Additionally, the prevention of the action ofmicroorganisms can be brought about by preservatives such as variousantibacterial and antifungal agents, including but not limited toparabens (e.g., methylparabens, propylparabens), chlorobutanol, phenol,sorbic acid, thimerosal or combinations thereof.

In a specific embodiment of the present disclosure, the composition iscombined or mixed thoroughly with a semi-solid or solid carrier. Themixing can be carried out in any convenient manner such as grinding.Stabilizing agents can be also added in the mixing process in order toprotect the composition from loss of therapeutic activity, i.e.,denaturation in the stomach. Examples of stabilizers for use in thecomposition include buffers, amino acids such as glycine and lysine,carbohydrates such as dextrose, mannose, galactose, fructose, lactose,sucrose, maltose, sorbitol, mannitol, etc.

In certain embodiments, the use of lipid delivery vehicles (e.g.,liposomes) is contemplated for the formulation and administration ofagents disclosed herein, or expression cassettes coding therefor. Theformation and use of liposomes is generally known to those of skill inthe art, and is also described below. Liposomes are formed fromphospholipids that are dispersed in an aqueous medium and spontaneouslyform multilamellar concentric bilayer vesicles (also termedmultilamellar vesicles (MLVs). MLVs generally have diameters of from 25nm to 4 μm. Sonication of MLVs results in the formation of smallunilamellar vesicles (SUVs) with diameters in the range of 200-500 Å,containing an aqueous solution in the core.

The following information can also be utilized in generating liposomalformulations. Phospholipids can form a variety of structures other thanliposomes when dispersed in water, depending on the molar ratio of lipidto water. At low ratios the liposome is the recommended structure. Thephysical characteristics of liposomes depend on pH, ionic strength andthe presence of divalent cations. Liposomes can show low permeability toionic and polar substances, but at elevated temperatures undergo a phasetransition which markedly alters their permeability. The phasetransition involves a change from a closely packed, ordered structure,known as the gel state, to a loosely packed, less-ordered structure,known as the fluid state. This occurs at a characteristicphase-transition temperature and results in an increase in permeabilityto ions, sugars and drugs. Liposomes may also be characterized by thetype of lipid they comprise—positively charged, negatively charged ornetural lipids.

Liposomes interact with cells via four different mechanisms: Endocytosisby phagocytic cells of the reticuloendothelial system such asmacrophages and neutrophils; adsorption to the cell surface, either bynonspecific weak hydrophobic or electrostatic forces, or by specificinteractions with cell-surface components; fusion with the plasma cellmembrane by insertion of the lipid bilayer of the liposome into theplasma membrane, with simultaneous release of liposomal contents intothe cytoplasm; and by transfer of liposomal lipids to cellular orsubcellular membranes, or vice versa, without any association of theliposome contents. Varying the liposome formulation can alter whichmechanism is operative, although more than one can operate at the sametime.

Examples of lipids include compounds that contain long-chain aliphatichydrocarbons and their derivatives. A lipid may be naturally-occurringor synthetic (i.e., designed or produced by man). Lipids are well knownin the art, and include for example, neutral fats, phospholipids,phosphoglycerides, steroids, terpenes, lysolipids, glycosphingolipids,glycolipids, sulphatides, lipids with ether and ester-linked fatty acidsand polymerizable lipids, and combinations thereof.

One of ordinary skill in the art would be familiar with the range oftechniques that can be employed for dispersing a composition in a lipidvehicle. For example, the CLEC11a or agonist thereof may be dispersed ina solution containing a lipid, dissolved with a lipid, emulsified with alipid, mixed with a lipid, combined with a lipid, covalently bonded to alipid, contained as a suspension in a lipid, contained or complexed witha micelle or liposome, or otherwise associated with a lipid or lipidstructure by any means known to those of ordinary skill in the art. Thedispersion may or may not result in the formation of liposomes.

The actual dosage amount of a composition of the present disclosureadministered to an animal patient can be determined by physical andphysiological factors such as body weight, severity of condition, thetype of disease being treated, previous or concurrent therapeuticinterventions, idiopathy of the patient and on the route ofadministration. Depending upon the dosage and the route ofadministration, the number of administrations of a preferred dosageand/or an effective amount may vary according to the response of thesubject. The practitioner responsible for administration will, in anyevent, determine the concentration of active ingredient(s) in acomposition and appropriate dose(s) for the individual subject.

In certain embodiments, pharmaceutical compositions may comprise, forexample, at least about 0.1% of CLEC11a or agonist thereof, about 0.5%of CLEC11a or agonist thereof, or about 1.0% of CLEC11a or agonistthereof. In other embodiments, the CLEC11a or agonist thereof maycomprise between about 2% to about 75% of the weight of the unit, orbetween about 25% to about 60%, for example, and any range derivabletherein. Naturally, the amount of the CLEC11a or agonist thereof in eachtherapeutically useful composition may be prepared is such a way that asuitable dosage will be obtained in any given unit dose of the compound.Factors such as solubility, bioavailability, biological half-life, routeof administration, product shelf life, as well as other pharmacologicalconsiderations will be contemplated by one skilled in the art ofpreparing such pharmaceutical formulations, and as such, a variety ofdosages and treatment regimens may be desirable.

In other non-limiting examples, a dose of CLEC11a or agonist thereof mayalso comprise from about 0.1 microgram/kg/body weight, about 0.2microgram/kg/body weight, about 0.5 microgram/kg/body weight, about 1microgram/kg/body weight, about 5 microgram/kg/body weight, about 10microgram/kg/body weight, about 50 microgram/kg/body weight, about 100microgram/kg/body weight, about 200 microgram/kg/body weight, about 350microgram/kg/body weight, about 500 microgram/kg/body weight, about 1milligram/kg/body weight, about 5 milligram/kg/body weight, about 10milligram/kg/body weight, about 50 milligram/kg/body weight, about 100milligram/kg/body weight, about 200 milligram/kg/body weight, about 350milligram/kg/body weight, about 500 milligram/kg/body weight, to about1000 mg/kg/body weight or more per administration, and any rangederivable therein. In non-limiting examples of a derivable range fromthe numbers listed herein, a range of about 5 mg/kg/body weight to about100 mg/kg/body weight, about 5 microgram/kg/body weight to about 500milligram/kg/body weight, etc., can be administered, based on thenumbers described above.

In particular embodiments of the present disclosure, the CLEC11a oragonist thereof are formulated to be administered via an alimentaryroute. Alimentary routes include all possible routes of administrationin which the composition is in direct contact with the alimentary tract.Specifically, the pharmaceutical compositions disclosed herein may beadministered orally, buccally, rectally, or sublingually. As such, thesecompositions may be formulated with an inert diluent or with anassimilable edible carrier, or they may be enclosed in hard- orsoft-shell gelatin capsule, or they may be compressed into tablets, orthey may be incorporated directly with the food of the diet.

In certain embodiments, the active compounds may be incorporated withexcipients and used in the form of ingestible tablets, buccal tablets,troches, capsules, elixirs, suspensions, syrups, wafers, and the like.The tablets, troches, pills, capsules and the like may also contain thefollowing: a binder, such as, for example, gum tragacanth, acacia,cornstarch, gelatin or combinations thereof; an excipient, such as, forexample, dicalcium phosphate, mannitol, lactose, starch, magnesiumstearate, sodium saccharine, cellulose, magnesium carbonate orcombinations thereof; a disintegrating agent, such as, for example, cornstarch, potato starch, alginic acid or combinations thereof; alubricant, such as, for example, magnesium stearate; a sweetening agent,such as, for example, sucrose, lactose, saccharin or combinationsthereof; a flavoring agent, such as, for example peppermint, oil ofwintergreen, cherry flavoring, orange flavoring, etc. When the dosageunit form is a capsule, it may contain, in addition to materials of theabove type, a liquid carrier. Various other materials may be present ascoatings or to otherwise modify the physical form of the dosage unit.For instance, tablets, pills, or capsules may be coated with shellac,sugar, or both. When the dosage form is a capsule, it may contain, inaddition to materials of the above type, carriers such as a liquidcarrier. Gelatin capsules, tablets, or pills may be enterically coated.Enteric coatings prevent denaturation of the composition in the stomachor upper bowel where the pH is acidic. See, e.g., U.S. Pat. No.5,629,001. Upon reaching the small intestines, the basic pH thereindissolves the coating and permits the composition to be released andabsorbed by specialized cells, e.g., epithelial enterocytes and Peyer'spatch M cells. A syrup of elixir may contain the active compound sucroseas a sweetening agent methyl and propylparabens as preservatives, a dyeand flavoring, such as cherry or orange flavor. Of course, any materialused in preparing any dosage unit form should be pharmaceutically pureand substantially non-toxic in the amounts employed. In addition, theactive compounds may be incorporated into sustained-release preparationand formulations.

For oral administration, such as in the treatment of periodontaldisease, the compositions of the present disclosure may alternatively beincorporated with one or more excipients in the form of a mouthwash,dentifrice, buccal tablet, oral spray, gel or sublingualorally-administered formulation. For example, a mouthwash may beprepared incorporating the active ingredient in the required amount inan appropriate solvent, such as a sodium borate solution (Dobell'sSolution). Alternatively, the active ingredient may be incorporated intoan oral solution such as one containing sodium borate, glycerin andpotassium bicarbonate, or dispersed in a dentifrice, or added in atherapeutically-effective amount to a composition that may includewater, binders, abrasives, flavoring agents, foaming agents, andhumectants. Alternatively the compositions may be fashioned into atablet, gel or solution form that may be placed under the tongue, alongthe gum line, brushed on to teeth surfaces, or otherwise dissolved inthe mouth. U.S. Pat. Nos. 6,074,674 and 6,270,750, both incorporated byreference, describe topical, sustained release compositions forperiodontal procedures.

In further embodiments, CLEC11a or agonist thereof may be administeredvia a parenteral route. As used herein, the term “parenteral” includesroutes that bypass the alimentary tract. Specifically, thepharmaceutical compositions disclosed herein may be administered forexample, but not limited to intravenously, intradermally,intramuscularly, intraarterially, intrathecally, subcutaneous, orintraperitoneally U.S. Pat. Nos. 6,537,514, 6,613,308, 5,466,468,5,543,158; 5,641,515; and 5,399,363 (each specifically incorporatedherein by reference in its entirety). Solutions of the active compoundsas free base or pharmacologically acceptable salts may be prepared inwater suitably mixed with a surfactant, such as hydroxypropylcellulose.Dispersions may also be prepared in glycerol, liquid polyethyleneglycols, and mixtures thereof and in oils. Under ordinary conditions ofstorage and use, these preparations contain a preservative to preventthe growth of microorganisms. The pharmaceutical forms suitable forinjectable use include sterile aqueous solutions or dispersions andsterile powders for the extemporaneous preparation of sterile injectablesolutions or dispersions (U.S. Pat. No. 5,466,468, specificallyincorporated herein by reference in its entirety). In all cases the formmust be sterile and must be fluid to the extent that easy injectabilityexists. It must be stable under the conditions of manufacture andstorage and must be preserved against the contaminating action ofmicroorganisms, such as bacteria and fungi. The carrier can be a solventor dispersion medium containing, for example, water, ethanol, polyol(i.e., glycerol, propylene glycol, and liquid polyethylene glycol, andthe like), suitable mixtures thereof, and/or vegetable oils. Properfluidity may be maintained, for example, by the use of a coating, suchas lecithin, by the maintenance of the required particle size in thecase of dispersion and by the use of surfactants. The prevention of theaction of microorganisms can be brought about by various antibacterialand antifungal agents, for example, parabens, chlorobutanol, phenol,sorbic acid, thimerosal, and the like. In many cases, it may bedesirable to include isotonic agents, for example, sugars or sodiumchloride. Prolonged absorption of the injectable compositions can bebrought about by the use in the compositions of agents delayingabsorption, for example, aluminum monostearate and gelatin.

For parenteral administration in an aqueous solution, for example, thesolution should be suitably buffered if necessary and the liquid diluentfirst rendered isotonic with sufficient saline or glucose. Theseparticular aqueous solutions are especially suitable for intravenous,intramuscular, subcutaneous, and intraperitoneal administration. In thisconnection, sterile aqueous media that can be employed will be known tothose of skill in the art in light of the present disclosure. Forexample, one dosage may be dissolved in 1 ml of isotonic NaCl solutionand either added to 1000 ml of hypodermoclysis fluid or injected at theproposed site of infusion, (see for example, “Remington's PharmaceuticalSciences” 15th Edition, pages 1035-1038 and 1570-1580). Some variationin dosage will necessarily occur depending on the condition of thesubject being treated. The person responsible for administration will,in any event, determine the appropriate dose for the individual subject.Moreover, for human administration, preparations should meet sterility,pyrogenicity, general safety and purity standards as required by FDAOffice of Biologics standards.

Sustained release formulations for treating of bone conditions includeU.S. Pat. Nos. 4,722,948, 4,843,112, 4,975,526, 5,085,861, 5,162,114,5,741,796 and 6,936,270, all of which are incorporated by reference.Methods and injectable compositions for bone repair are described inU.S. Pat. Nos. 4,863,732, 5,531,791, 5,840,290, 6,281,195, 6,288,043,6,485,754, 6,662,805 and 7,008,433, all of which are incorporated byreference.

Sterile injectable solutions are prepared by incorporating the activecompounds in the required amount in the appropriate solvent with variousof the other ingredients enumerated above, as required, followed byfiltered sterilization. Generally, dispersions are prepared byincorporating the various sterilized active ingredients into a sterilevehicle which contains the basic dispersion medium and the requiredother ingredients from those enumerated above. In the case of sterilepowders for the preparation of sterile injectable solutions, thepreferred methods of preparation are vacuum-drying and freeze-dryingtechniques which yield a powder of the active ingredient plus anyadditional desired ingredient from a previously sterile-filteredsolution thereof. A powdered composition is combined with a liquidcarrier such as, e.g., water or a saline solution, with or without astabilizing agent.

In particular, it is contemplated that delivery of CLEC11a or agonistsor mimics thereof will be achieved through a slow release deliverysystem, which are well known in the art. These formulations are ofparticular relevance in treating bone fractures, in spinal fusion, or inthe systemic treatment of osteoporosis (i.e., bone repair). A hydrogelis a network of polymer chains that are hydrophilic, sometimes found asa colloidal gel in which water is the dispersion medium. Hydrogels arehighly absorbent (they can contain over 90% water) natural or syntheticpolymeric networks. Hydrogels also possess a degree of flexibility verysimilar to natural tissue, due to their significant water content.Common uses for hydrogels include scaffolds in tissue engineering andsustained-release drug delivery systems.

B. Devices

In addition to providing CLEC11a or agonist thereof for administrationby routes discussed above, such agents, alone or in combination, maybeused in the context of devices, such as implants. A variety of bonerelated implants are contemplated, including dental implants, jointimplants such as hips, knees, and elbows, vertebral/spinal implants, andothers. The CLEC11a or agonist thereof may be impregnated in a surfaceof the implant, including in a bioactive matrix or coating. Theinhibitor may be further formulated to sustained, delayed, prolonged ortime release. The coating may comprise polymers, for example, such asthose listed below. The following is a list of U.S. patents relating tobone implants and devices which may be utilized in accordance with thisembodiment of the disclosure:

TABLE 3 U.S. Pat. No.* Patent Title 7,044,972 Bone implant, inparticular, an inter-vertebral implant 7,022,137 Bone hemi-lumbarinterbody spinal fusion implant having an asymmetrical leading end andmethod of installation thereof 7,001,551 Method of forming a compositebone material implant 6,994,726 Dual function prosthetic bone implantand method for preparing the same 6,989,031 Hemi-interbody spinalimplant manufactured from a major long bone ring or a bone composite6,988,015 Bone implant 6,981,975 Method for inserting a spinal fusionimplant having deployable bone engaging projections 6,981,872 Boneimplant method of implanting, and kit for use in making implants,particularly useful with respect to dental implants 6,929,662 End memberfor a bone fusion implant 6,923,830 Spinal fusion implant havingdeployable bone engaging projections 6,921,264 Implant to be implantedin bone tissue or in bone tissue supplemented with bone substitutematerial 6,918,766 Method, arrangement and use of an implant forensuring delivery of bioactive substance to the bone and/or tissuesurrounding the implant 6,913,621 Flexible implant using partiallydemineralized bone 6,899,734 Modular implant for fusing adjacent bonestructure 6,860,884 Implant for bone connector 6,852,129 Adjustable bonefusion implant and method 6,802,845 Implant for bone connector 6,786,908Bone fracture support implant with non-metal spacers 6,767,367 Spinalfusion implant having deployable bone engaging projections 6,761,738Reinforced molded implant formed of cortical bone 6,755,832 Bone plateimplant 6,730,129 Implant for application in bone, method for producingsuch an implant, and use of such an implant 6,689,167 Method of usingspinal fusion device, bone joining implant, and vertebral fusion implant6,689,136 Implant for fixing two bone fragments to each other 6,666,890Bone hemi-lumbar interbody spinal implant having an asymmetrical leadingend and method of installation thereof 6,652,592 Segmentallydemineralized bone implant 6,648,917 Adjustable bone fusion implant andmethod 6,607,557 Artificial bone graft implant 6,599,322 Method forproducing undercut micro recesses in a surface, a surgical implant madethereby, and method for fixing an implant to bone 6,562,074 Adjustablebone fusion implant and method 6,562,073 Spinal bone implant D473,944Bone implant 6,540,770 Reversible fixation device for securing animplant in bone 6,537,277 Implant for fixing a bone plate 6,506,051 Boneimplant with intermediate member and expanding assembly 6,478,825Implant, method of making same and use of the implant for the treatmentof bone defects 6,458,136 Orthopaedic instrument for sizing implantsites and for pressurizing bone cement and a method for using the same6,447,545 Self-aligning bone implant 6,436,146 Implant for treatingailments of a joint or a bone 6,371,986 Spinal fusion device, bonejoining implant, and vertebral fusion implant 6,370,418 Device andmethod for measuring the position of a bone implant 6,364,880 Spinalimplant with bone screws 6,350,283 Bone hemi-lumbar interbody spinalimplant having an asymmetrical leading end and method of installationthereof 6,350,126 Bone implant 6,287,343 Threaded spinal implant withbone ingrowth openings 6,270,346 Dental implant for bone regrowth6,248,109 Implant for interconnecting two bone fragments 6,217,617 Boneimplant and method of securing 6,214,050 Expandable implant forinter-bone stabilization and adapted to extrude osteogenic material, anda method of stabilizing bones while extruding osteogenic material6,213,775 Method of fastening an implant to a bone and an implanttherefor 6,206,923 Flexible implant using partially demineralized bone6,203,545 Implant for fixing bone fragments after an osteotomy 6,149,689Implant as bone replacement 6,149,688 Artificial bone graft implant6,149,686 Threaded spinal implant with bone ingrowth openings 6,126,662Bone implant 6,083,264 Implant material for replacing or augmentingliving bone tissue involving thermoplastic syntactic foam 6,058,590Apparatus and methods for embedding a biocompatible material in apolymer bone implant 6,018,094 Implant and insert assembly for bone anduses thereof 5,976,147 Modular instrumentation for bone preparation andimplant trial reduction of orthopedic implants 5,906,488 Releasableholding device preventing undesirable rotation during tightening of ascrew connection in a bone anchored implant 5,899,939 Bone-derivedimplant for load-supporting applications 5,895,425 Bone implant5,890,902 Implant bone locking mechanism and artificial periodontalligament system 5,885,287 Self-tapping interbody bone implant 5,819,748Implant for use in bone surgery 5,810,589 Dental implant abutmentcombination that reduces crestal bone stress 5,759,035 Bone fusiondental implant with hybrid anchor 5,720,750 Device for the preparationof a tubular bone for the insertion of an implant shaft 5,709,683Interbody bone implant having conjoining stabilization features for bonyfusion 5,709,547 Dental implant for anchorage in cortical bone 5,674,725Implant materials having a phosphatase and an organophosphorus compoundfor in vivo mineralization of bone 5,658,338 Prosthetic modular bonefixation mantle and implant system D381,080 Combined metallic skull basesurgical implant and bone flap fixation plate 5,639,402 Method forfabricating artificial bone implant green parts 5,624,462 Bone implantand method of securing D378,314 Bone spinal implant 5,607,430 Bonestabilization implant having a bone plate portion with integral cableclamping means 5,571,185 Process for the production of a bone implantand a bone implant produced thereby 5,456,723 Metallic implantanchorable to bone tissue for replacing a broken or diseased bone5,441,538 Bone implant and method of securing 5,405,388 Bone biopsyimplant 5,397,358 Bone implant 5,383,935 Prosthetic implant withself-generated current for early fixation in skeletal bone 5,364,268Method for installing a dental implant fixture in cortical bone5,312,256 Dental implant for vertical penetration, adapted to differentdegrees of hardness of the bone *The preceding patents are all herebyincorporated by reference in their entirety.

V. EXAMPLES

The following examples are included to further illustrate variousaspects of the disclosure. It should be appreciated by those of skill inthe art that the techniques disclosed in the examples which followrepresent techniques and/or compositions discovered by the inventor tofunction well in the practice of the disclosure, and thus can beconsidered to constitute preferred modes for its practice. However,those of skill in the art should, in light of the present disclosure,appreciate that many changes can be made in the specific embodimentswhich are disclosed and still obtain a like or similar result withoutdeparting from the spirit and scope of the disclosure.

Example 1—Materials and Methods

Mice.

To generate Clec11a^(−/−) mice, Cas9 mRNA and sgRNAs were transcribedusing mMESSAGE mMACHINE T7 Ultra Kit and MEGAshortscript Kit (Ambion),purified by MEGAclear Kit (Ambion), and microinjected into C57BL/6zygotes by the Transgenic Core Facility of the University of TexasSouthwestern Medical Center (UTSW). Chimeric mice were genotyped byrestriction fragment length polymorphism (RFLP) analysis and backcrossedonto a C57BL/Ka background to obtain germline transmission. Mutant micewere backcrossed onto a C57BL/Ka background for 3 to 6 generations priorto analysis. Wild-type C57BL/Ka mice were used for rClec11a injection,ovariectomy, and dexamethasone injection experiments. All procedureswere approved by the UTSW Institutional Animal Care and Use Committee.

Flow Cytometry.

Antibodies used to analyze hematopoietic stem cells (HSCs) andmultipotent hematopoietic progenitors (MPPs) included anti-CD150-PE-Cy5(BioLegend, clone TC15-12F12.2, 1:200), anti-CD48-FITC (eBioscience,clone HM48-1, 1:200), anti-Sca-1-PEcy7 (eBioscience, E13-161.7, 1:200),anti-c-Kit-APC-eFluor780 (eBioscience, clone 2B8, 1:200) and thefollowing antibodies against lineage markers: anti-Ter119-PE(eBioscience, clone TER-119, 1:200), anti-B220-PE (BioLegend, clone 6B2,1:400), anti-Gr-1-PE (BioLegend, clone 8C5, 1:800), anti-CD2-PE(eBioscience, clone RM2-5, 1:200), anti-CD3-PE (BioLegend, clone 17A2,1:200), anti-CD5-PE (BioLegend, clone 53-7.3, 1:400) and anti-CD8-PE(eBioscience, clone 53-6.7, 1:400). The following antibodies were usedto identify restricted hematopoietic progenitors: anti-CD34-FITC(eBioscience, clone RAM34, 1:100); anti-CD16/32-Alexa Fluor 700(eBioscience, clone 93, 1:200); anti-CD135-PEcy5 (eBioscience, cloneA2F10, 1:100); anti-CD127-Biotin (BioLegend, clone A7R34,1:200)+Streptavidin-PE-CF592 (BD Biosciences, 1:500);anti-cKit-APC-eFluor780 (eBioscience, clone 2B8, 1:200); anti-ScaI-PEcy7(eBioscience, clone E13-161.7, 1:200) and lineage markers listed above.The following antibodies were used to identify differentiated cells:anti-CD71-FITC (BD Biosciences, clone C2, 1:200); anti-Ter119-APC(eBioscience, clone TER-119, 1:200); anti-CD3-PE (BioLegend, clone 17A2,1:200); anti-B220-PEcy5 (eBioscience, clone RA3-6B2, 1:400);anti-Mac-1-APC-eFluor780 (eBioscience, M1/70, 1:200) and anti-Gr-1-PEcy7(BioLegend, clone RB6-8C5, 1:400). Anti-CD45.2-FITC (BioLegend, clone104, 1:200) and anti-CD45.1-APC-eFluor-78 (eBioscience, clone A20,1:100) were used to distinguish donor from recipient cells incompetitive reconstitution assays. The following antibodies were used toidentify SSCs: anti-CD45-FITC (eBioscience, clone 30-F11, 1:200),anti-Ter119-FITC (eBioscience, clone TER-119, 1:200), anti-CD31-FITC(Biolegend, clone MEC13.3, 1:200) and anti-PDGFRα-biotin (eBioscience,clone APA5, 1:200). Cells were stained with antibodies in 200 μl ofstaining medium (HBSS+2% fetal bovine serum) on ice for 1 hour, and thenwashed by adding 2 ml of staining buffer followed by centrifugation.Biotin-conjugated antibodies were incubated with streptavidin-PE foranother 20 minutes (Biolegend, 1:500). Cells were resuspended instaining medium with 1 μg/ml DAPI (Invitrogen) and analyzed with aFACSCanto flow cytometer (BD Biosciences) or sorted using a FACSAriaflow cytometer (BD Biosciences) with a 130 μm nozzle.

Long-Term Competitive Reconstitution Assays in Irradiated Mice.

Two month-old adult recipient mice were irradiated with an XRAD 320irradiator (Precision X-Ray Inc.), giving two doses of 550 rad,delivered at least 2 hours apart. C57BL/Ka-Thy-1.1 (CD45.2) donor miceand C57BL/Ka-Thy-1.2(CD45.1) recipient mice were used in transplantexperiments. 300,000 donor whole bone marrow cells from Clec11a^(−/−) orlittermate control mice (CD45.2) were transplanted along with 300,000recipient whole bone marrow cells (CD45.1) into lethally irradiatedrecipient mice (C57BL/Ka-Thy-1.1×C57BL/Ka-Thy-1.2 (CD45.1/CD45.2)heterozygotes). Peripheral blood was obtained from the tail veins ofrecipient mice at 4 to 16 weeks after transplantation. Blood wassubjected to ammonium-chloride lysis of the red blood cells andleukocytes were stained with antibodies against CD45.1, CD45.2, B220,Mac-1, CD3 and Gr-1 to assess hematopoietic chimerism by donor andrecipient cells by flow cytometry.

Bone Sectioning and Immunostaining.

Dissected bones were fixed in 4% paraformaldehyde overnight, decalcifiedin 10% EDTA for 4 days, and dehydrated in 30% sucrose for 2 days. Boneswere sectioned (10 μm) using the CryoJane tape-transfer system (Leica).Sections were blocked in PBS with 10% horse serum for 30 minutes andthen stained overnight at 4° C. with goat anti-Clec11a antibody (R&Dsystems, 1:500), rabbit anti-Aggrecan antibody (Chemicon, 1:500), rabbitanti-Perilipin antibody (Sigma, 1:2000) or goat anti-Osteopontinantibody (R&D, 1:500). Donkey anti-goat Alexa Fluor 488 and donkeyanti-rabbit Alexia Fluor 555 were used as secondary antibodies(Invitrogen, 1:500). Slides were mounted with anti-fade prolong goldwith DAPI (Invitrogen). Images were acquired using a Zeiss LSM780confocal microscope or Olympus IX81 microscope.

Bone Marrow Digestion and Stromal Cell Differentiation.

Enzymatic digestion of bone marrow cells and CFU-F culture wereperformed as described previously (Suire et al., 2012). Briefly, intactmarrow plugs were flushed from the long bones and subjected to tworounds of enzymatic digestion at 37° C. for 15 minutes each. Thedigestion buffer contained 3 mg/ml type I collagenase (Worthington), 4mg/ml dispase (Roche Diagnostics) and 1 U/ml DNAse I (Sigma) in HBSSwith calcium and magnesium. The digested marrow cells were pooled intostaining medium (HBSS+2% fetal bovine serum) with 2 mM EDTA to stop theenzymatic reaction. Freshly digested single-cell suspensions were platedat a density of 5×10⁶ cells in 10 cm plates with DMEM (Gibco) plus 20%fetal bovine serum (Sigma F2442, lot number 14M255; specific lots wereselected for the ability to support CFU-F growth), 10 μM ROCK inhibitor(Y-27632, TOCRIS), and 1% penicillin/streptomycin (Invitrogen). Cellcultures were maintained at 37° C. in gas-tight chambers(Billups-Rothenberg, Del Mar, Calif.) that were flushed daily for 30seconds with 5% O₂ and 5% CO₂ (balance Nitrogen) to enhance progenitorsurvival and proliferation (Morrison et al., 2000). Differentiation wasassessed by replating primary CFU-F cells into 48-well plates (25,000cells/cm²). On the second day of culture, the medium was replaced withadipogenic (4 days), osteogenic (7 days or 14 days), or chondrogenicdifferentiation (14 days) medium (StemPro MSC differentiation kits; LifeTechnologies). Adipogenic differentiation was quantified by Oil Red 0staining (Sigma). Osteogenic differentiation was quantified by StemTAGAlkaline Phosphatase Staining and Activity Assay Kit (Cell Biolabs) andalizarin red staining (Sigma). Chondrogenic differentiation wasquantified by toluidine blue staining (Sigma). Osteogenicdifferentiation of MC3T3-E1 cells was performed using the StemProosteogenesis differentiation kit (Life Technologies). Images wereacquired using an Olympus IX81 microscope.

MicroCT Analysis.

Femurs and lumbar vertebrae were dissected, fixed overnight in 4%paraformaldehyde and stored in 70% ethanol at 4° C. The bones werescanned at an isotropic voxel size of 3.5 μm and 7 μm, respectively, atthe Texas A&M University Baylor College of Dentistry (μCT 35; ScancoMedical AG, Bassersdorf, Switzerland). Trabecular bone parameters weremeasured by analyzing 100 slices in the distal metaphysis of femurs nearthe growth plate. Cortical bone parameters were measured by analyzing100 slices in mid-diaphysis femurs. Vertebral bone parameters weremeasured by analyzing 200 slices in ventral L3 lumbar vertebrae.

Calcein Double Labeling and Histomorphometry Analysis.

On day 0 and day 7, mice were injected intraperitoneally with 10 mg/kgbody mass calcein dissolved in calcein buffer (0.15 M NaCl plus 2%NaHCO₃ in water) and sacrificed on day 9. The tibias were fixedovernight in 4% paraformaldehyde at 4° C., dehydrated in 30% sucrose for2 days and sectioned without decalcification (7 μm sections). Mineralapposition and bone formation rates were determined as previouslydescribed (Egan et al., 2012). For the quantification of osteoblastnumber/bone surface and osteoclast number/bone surface, decalcified 10μm femur sections were stained histochemically for alkaline phosphatase(Roche) or tartrate-resistant acid phosphatase (Sigma) activity. Growthplate chondrocytes were identified based on staining with safraninO/fast green and quantified using Image J.

Bone Fractures.

A stainless steel wire was inserted into the intramedullary canal of thefemur through the knee after anesthesia, and a bone fracture wasintroduced in the femur mid-diaphysis by 3-point bending. Buprenorphinewas injected every 12 hours up to 72 hours after the surgery.

Bone Resorption Analysis.

Bone resorption rate was determined by measuring urinary levels ofdeoxypyridinoline (DPD) using a MicroVue DPD ELISA Kit (Quidel)according to the manufacturer's instructions. The DPD values werenormalized to urinary creatinine levels using the MicroVue CreatinineAssay Kit (Quidel).

Recombinant Protein Purification.

Mouse Clec11a cDNA was cloned into pcDNA3 vector (Invitrogen) containinga C-terminal 1× Flag-tag, which was then transfected into HEK293 cellswith Lipofectamine 2000 (Invitrogen) and subjected to stable cell lineselection using 1 mg/ml G418 (Sigma). Stable clones with high Clec11aexpression were cultured in DMEM plus 10% FBS (Sigma), and 1%penicillin/streptomycin (Invitrogen). Culture medium was collected everytwo days, centrifuged to eliminate cellular debris, and stored with 1 mMphenylmethylsulfonyl fluoride at 4° C. to inhibit protease activity.rClec11a was purified using ANTI-FLAG M2 Affinity Gel (Sigma), andeluted using 100 μg/ml 3× FLAG peptide in elution buffer (50 mM HEPES,150 mM NaCl and 10% glycerol, pH=7.5). Eluted protein was concentratedby Amicon Ultra-15 Centrifugal Filter Units (Millipore), quantified bySDS-PAGE, and stored at −80° C.

Osteoporosis Model.

For ovariectomy-induced osteoporosis, 8 week-old virgin female mice wereanesthetized using Isoflurane, shaved, and disinfected with Betadine. Adorsal midline incision was made and the periovarian fat pad was gentlygrasped to exteriorize the ovary. The fallopian tube was then clampedoff and the ovary was removed by cutting above the clamped area. Theuterine horn was returned into the abdomen and the same process wasrepeated on the other side. After surgery, buprenorphine was given foranalgesia, and mice were closely monitored until they resumed fullactivity. Vehicle, 40 μg/kg PTH (1-34) or 50 μg/kg rClec11a weresubcutaneously injected daily starting one day after the surgery andcontinuing for 28 days then the mice were analyzed. Fordexamethasone-induced osteoporosis, PBS or 20 mg/kg dexamethasone wasinjected peritoneally into 8 week-old virgin female mice daily for 28days. Vehicle, 40 μg/kg PTH (1-34) or 50 μg/kg rClec11a weresubcutaneously injected at the same time.

qPCR and RNA-seq.

For quantitative reverse transcription PCR (qPCR), 6000PDGFRα⁺CD45⁻Ter119⁻CD31⁻ cells were flow cytometrically sorted fromenzymatically dissociated bone marrow into Trizol (Invitrogen). RNA wasextracted and reverse transcribed into cDNA using SuperScript III(Invitrogen). qPCR was performed using a Roche LightCycler 480. Theprimers for Clec11a mRNA were: 5′-AGG TCC TGG GAG GGA GTG-3′ (Forward;SEQ ID NO: 1) and 5′-GGG CCT CCT GGA GAT TCT T-3′ (Reverse; SEQ ID NO:2). The primers for Actb mRNA were: 5′-GCT CTT TTC CAG CCT TCC TT-3′(Forward; SEQ ID NO: 3) and 5′-CTT CTG CAT CCT GTC AGC AA-3′ (Reverse;SEQ ID NO: 4). For RNA-seq experiments, extracted RNAs were digestedwith DNAse I (Ambion) and purified with RNeasy MinElute Spin Columns(Qiagen). RNAs were then linearly amplified into double stranded cDNAusing the Ovation RNA-seq V2 system (NuGEN). RNA-seq libraries wereconstructed using Ovation Ultralow System V2 1-16 (NuGEN) and sequencedusing an Illumina HiSeq 2500 sequencer (100 bp paired-end) at the NextGeneration Sequencing Core in the UTSW McDermott Center.

Statistical Analysis.

The statistical significance of differences between two treatments wasassessed using two-tailed Student's t tests. The statisticalsignificance of differences among more than two groups was assessedusing one-way ANOVAs with Tukey's multiple comparison tests. Thestatistical significance of differences in long-term competitivereconstitution assays was assessed using two-way ANOVAs with Sidak'smultiple comparison tests. All data represent mean±SD. *P<0.05,**P<0.01, ***P<0.001.

Blood Cell Counts.

Peripheral blood was collected from the tail vein using Microvette CB300 K2E tubes (Sarstedt) and counted using a HEMAVET HV950 cell counter(Drew Scientific).

Hematopoietic Colony Formation.

Hematopoietic colony formation was assessed by seeding 20,000unfractionated mouse femur bone marrow cells into MethoCult M3334 orMethoCult M3234 supplemented with 10 ng/ml GM-CSF (STEMCELLTechnologeis). The cultures were incubated at 37° C. for 10 days andthen colonies were counted under the microscope.

Biomechanical Analysis.

To assess biomechanical properties, femurs were rehydrated in PBS for atleast 3 hours before testing. The femurs were preconditioned with 20cycles of bending displacement (0.1 mm) and then loaded to failure with3-point bending (each holding point was 4 mm from the middle breakpoint) under displacement control (0.05 mm/sec) using a material testingsystem (Instron model #5565, Norwood, Mass.).

Genotyping.

To genotype Clec11a^(+/+), Clec11^(+/−), and Clec11a^(−/−) mice thefollowing primers were used: 5′-TTT GGG TGC TGG GAA GCC C-3′ (SEQ ID NO:5) and 5′-TTG CAC TGA GTC GCG GGT G-3′ (SEQ ID NO: 6) (Clec11a^(+/+):910 bp; Clec11^(+/−) or Clec11a^(−/−): 538 bp). To distinguish betweenClec11a^(+/−) and Clec11a^(−/−) mice, the following primers were used:5′-GAG GAA GAG GAA ATC ACC ACA GC-3′ (SEQ ID NO: 7) and 5′-TTG CAC TGAGTC GCG GGT G-3′ (SEQ ID NO: 8) (Clec11a^(+/−): 482 bp; Clec11a^(−/−):no amplification product).

Example 2—Results

Clec11a is Highly Expressed by SSCs.

Reanalysis of our previously published microarray data (Ding et al.,2012) revealed that among enzymatically dissociated bone marrow cells,Clec11a is significantly more highly expressed byScf-GFP⁺CD45⁻Ter119⁻CD31⁻ stromal cells (which are highly enriched forLepR⁺ SSCs (Zhou et al., 2014)) and Col2.3-GFP⁺CD45⁻Ter119⁻CD31⁻osteoblasts as compared to VE-cadherin⁺ endothelial cells andunfractionated cells (FIG. 1A). The inventors confirmed this by RNAsequencing (FIG. 1B) and quantitative real-time PCR (qPCR) (FIG. 1C),each of which showed that Clec11a transcripts were at least 100-foldmore abundant in PDGFRα⁺CD45⁻Ter119⁻CD31⁻ cells andCol2.3-GFP⁺CD45⁻Ter119⁻CD31⁻ osteoblasts as compared to unfractionatedbone marrow cells (FIG. 1B and FIG. 1C).

To assess Clec11a protein expression, the inventors stained femursections from 8 week-old mice with a commercially-available polyclonalantibody against Clec11a. Clec11a protein was concentrated near thegrowth plate at the boundary between the growth plate and the bonemarrow, as well as around trabecular bones in the metaphysis (FIG. 1Dand FIG. 1E). Clec11a was also in the cortical bone matrix of the femurdiaphysis, with higher levels of staining near the periosteal surface(FIG. 1D and FIG. 1F). The level of Clec11a in cortical bone variedregionally within bones, with higher expression toward the femur neck ascompared to the distal femur. The inventors observed a similarexpression pattern in vertebrae, with anti-Clec11a antibody stainingaround trabecular bone and in cortical bone (FIG. 8E).

Clec11a is not Required for Hematopoiesis in Normal Mice.

To test the physiological function of Clec11a, the inventors usedCRISPR-Cas9 to generate a Clec11a mutant allele (Clec11a^(−/−)) bydeleting the second exon of Clec11a (FIG. 8A). They did this bydesigning guide RNAs against intron sequences flanking exon 2, leadingto the generation of a germline mutant allele lacking the second exon(FIG. 8A). This was predicted to be a strong loss of function allele asexon 2 deletion introduced a frame shift that created a premature stopcodon in exon 3 (FIG. 8B). The predicted mutant protein did not containany of the domains that are thought to be functionally important inClec11a, including the polyglutamic acid sequence, the alpha-helicalleucine zipper, or the C-type lectin domain (FIG. 8B). Deletion ofClec11a exon 2 in founder mice and germline transmission of the mutantallele were confirmed by PCR and sequencing of genomic DNA (FIG. 8C).Immunofluorescence analysis of femur sections with an anti-Clec11apolyclonal antibody suggested a complete loss of Clec11a protein fromClec11a^(−/−) mice (FIG. 1E and FIG. 1F).

Clec11a^(−/−) mice were born with the expected Mendelian frequency (FIG.8D) and appeared grossly normal (FIG. 1G), with normal body mass (FIG.1H) at 2 months of age. White blood cell, red blood cell, and plateletcounts were normal in 2 month-old, 10 month-old, and 16 month-oldClec11a^(−/−) mice (FIGS. 8F-8H).

Young adult Clec11a^(−/−) mice had normal bone marrow and spleencellularity (FIG. 1I), as well as normal frequencies of Mac1⁺Gr1⁺myeloid cells, Ter119⁺CD71⁺ erythroid progenitors, CD3⁺ T cells, andB220⁺ B cells in the bone marrow and spleen (FIGS. 1J-1M). Clec11a^(−/−)mice also had normal frequencies of CD150⁺CD48⁻Lineage⁻Sca-1⁺c-kit⁺ HSCs(Kiel et al., 2005), CD150⁻CD48⁻Lineage⁻Sca-1⁺c-kit⁺ multipotentprogenitors (MPPs) (Kiel et al., 2008; Oguro et al., 2013),CD34⁺FcγR⁺Lineage⁻Sca-1⁻c-kit⁺ granulocyte-macrophage progenitors(GMPs), CD34⁻FcγR⁻Lineage⁻Sca-1⁻c-kit⁺ megakaryocyte-erythrocyteprogenitors (MEPs), CD34⁺FcγR⁻Lineage⁻Sca-1⁻c-kit⁺ common myeloidprogenitors (CMPs) (Akashi et al., 2000) andFlt3⁺IL7Rα⁺Lineage⁻Sca-1^(low)c-kit^(low) common lymphoid progenitors(CLPs) (Kondo et al., 1997) in the bone marrow and spleen (FIGS. 1N-1P).Bone marrow from Clec11a^(−/−) mice gave normal levels of long-termmultilineage reconstitution upon transplantation into irradiated mice(FIGS. 1Q-1T). Clec11a is therefore not required for normalhematopoiesis in young adult mice.

Human recombinant Clec11a increases erythroid (BFU-E) and myeloid(CFU-G/M/GM) colony formation by human bone marrow cells when added toculture along with EPO or GM-CSF, respectively (Hiraoka et al., 1997;Hiraoka et al., 2001). In cultures of mouse bone marrow cells,recombinant mouse Clec11a did not significantly increase BFU-E colonyformation when added along with EPO and only slightly increasedCFU-G/M/GM colony formation when added along with GM-CSF (FIGS. 81 and8J).

Clec11a is Necessary for Osteogenesis.

To test whether Clec11a regulates osteogenesis, the inventors performedmicro-computed tomography (micro-CT) analysis of the distal femur fromsex-matched littermates. Trabecular bone volume was significantlyreduced (by 24±18%) in 2 month-old Clec11a^(−/−) mice as compared tolittermate controls (FIG. 2A and FIG. 2D; in no case did the inventorsobserve any significant difference between Clec11a^(+/+) andClec11a^(+/−) mice so samples from these mice were combined in thecontrols in all experiments). Clec11a^(−/−) mice had significantlyreduced trabecular bone thickness, increased trabecular spacing, anddecreased connectively density and bone mineral density (FIGS. 2D-2I).With the exception of the reduction in bone mineral density, thesedefects seemed to worsen with age as 10 and 16 month-old Clec11a^(−/−)mice exhibited a more profound reduction in trabecular bone volume(62±27% and 64±11%, respectively), trabecular number, trabecularthickness and connectivity density, as well as increased trabecularspacing (FIGS. 2B-2H).

MicroCT analysis of cortical bone parameters in the femur diaphysis fromsex-matched littermates did not show significant differences betweenClec11a^(−/−) and control mice at 2 or 10 months of age (FIGS. 9A and9B). However, 16 month-old Clec11a^(−/−) mice exhibited significantlyreduced cortical bone area, cortical area/total area ratio, and corticalthickness as compared to controls (FIGS. 9C-9H). When the inventorstested the mechanical strength of bones using a three point bendingtest, they found significantly reduced peak load and fracture energy inthe femur diaphysis of 2, 10, and 16 month-old Clec11a^(−/−) as comparedto sex-matched littermate control mice (FIGS. 91 and 9J).

To test whether other bones also exhibit defects in the absence ofClec11a, the inventors examined L3 lumbar vertebrae from Clec11a^(−/−)as compared to sex-matched littermate control mice. Micro-CT analysis ofthe vertebrae as a whole did not detect a difference betweenClec11a^(−/−) and sex-matched littermate control mice (data not shown).However, the inventors did observe a significant reduction in trabecularbone in the ventral portion of L3 vertebrae at 2, 10, and 16 months ofage (FIGS. 2J-2L). The inventors observed significantly reducedtrabecular bone volume and trabecular number, and significantlyincreased trabecular spacing in 2, 10 and 16 month-old Clec11a^(−/−) ascompared to sex-matched littermate control mice (FIGS. 2M-2P). Clec11ais therefore required to maintain bone in limb and vertebral bones.

To determine whether Clec11a regulates bone formation, the inventorsperformed calcein double labeling to assess the rate of trabecular boneformation (FIG. 2S). The trabecular bone mineral apposition andtrabecular bone formation rates were both significantly decreased in thefemur metaphysis of 2 and 10 month-old Clec11a^(−/−) as compared tosex-matched littermate control mice (FIG. 2T and FIG. 2U; 16 month-oldmice were not assessed in these experiments). In contrast, the urinarybone resorption marker deoxypyridinoline did not significantly differbetween Clec11a^(−/−) and sex-matched littermate control mice (FIG. 2V).This suggested that the difference in trabecular bone volume betweenClec11a^(−/−) and littermate control mice reflected reduced boneformation in adult mice rather than a change in bone resorption.

Clec11a is Necessary for Normal Osteogenic Differentiation.

To test whether Clec11a regulates the differentiation of SSCs, theinventors cultured CFU-F from enzymatically dissociated Clec11a^(−/−)and littermate control bone marrow cells, then replated equal numbers ofClec11a^(−/−) or control cells under osteogenic, adipogenic, orchondrogenic culture conditions. Consistent with the decreasedosteogenesis in vivo, fibroblasts from Clec11a^(−/−) mice gave rise tosignificantly fewer cells with alkaline phosphatase staining or alizarinred staining as compared to control fibroblasts under osteogenic cultureconditions (FIGS. 3A-3D). In contrast, under adipogenic (FIG. 3E andFIG. 3F) and chondrogenic (FIGS. 3G and 3H) culture conditions, theinventors did not detect any difference between Clec11a^(−/−) andcontrol cells in terms of the amount of oil red O or toluidine bluestaining. Clec11a was thus required for normal osteogenicdifferentiation but not for adipogenic or chondrogenic differentiationby bone marrow stromal cells in culture. Consistent with this, thenumber of Perilipin⁺ adipocytes (FIGS. 3I-3K) and Safranin chondrocytes(FIGS. 3L-3N) in femur sections from 2 month-old mice did not differbetween Clec11a^(−/−) and sex matched littermate control mice.

Clec11a is Necessary for Normal Fracture Healing.

To test whether Clec11a regulates fracture healing, the inventorsperformed mid-diaphyseal femur fractures in 2 month-old Clec11a^(−/−)and sex-matched littermate control mice. Two weeks after the fracture,Clec11a^(−/−) mice had significantly less callus bone around thefracture site (FIG. 4A) and significantly more callus cartilage (FIG.4B) as compared to controls, suggesting delayed endochondralossification. MicroCT analysis of the callus at the fracture site twoweeks after the fracture revealed significantly reduced trabecular bonevolume, trabecular number, trabecular thickness, and trabecularconnectivity density (FIGS. 4C-H) and significantly increased trabecularspacing (FIG. 4I) in Clec11a^(−/−) mice. The bone mineral density in thecallus did not significantly differ between Clec11a^(−/−) and controlmice (FIG. 4J). Therefore, fracture healing is compromised inClec11a^(−/−) mice.

Recombinant Clec11a Promotes Osteogenesis In Vitro and In Vivo.

To test whether Clec11a is sufficient to promote osteogenesis, theinventors constructed a HEK293 cell line that stably expressed mouseClec11a with a C-terminal Flag tag. They affinity purified recombinantClec11a (rClec11a) that had been secreted into the culture medium usinganti-Flag M2 beads. Unfractionated bone marrow cells from wild-type micewere cultured to form CFU-F, which were then replated and grown underosteogenic culture conditions. Addition of rClec11a to these culturessignificantly increased alizarin red staining, suggesting increasedmineralization (FIG. 5A and FIG. 5B). The inventors also transientlyexpressed mouse Clec11a cDNA in the MC3T3-E1 mouse pre-osteoblast cellline (Wang et al., 1999). MC3T3-E1 cells expressing Clec11a exhibitedincreased osteogenic differentiation in culture (FIG. 5C and FIG. 5D).

To test whether rClec11a promotes osteogenesis in vivo, the inventorsadministered daily subcutaneous injections of rClec11a to 2 month-oldwild-type mice for 28 days. Consistent with the in vitro data, rClec11adose-dependently increased trabecular bone volume in the distal femurmetaphysis (FIG. 5E and FIG. 5F). The higher doses of rClec11a alsosignificantly increased trabecular number and significantly reducedtrabecular spacing (FIGS. 5G-5I). The increased osteogenesis in miceadministered Clec11a was mainly due to increased bone formation (FIG.5J). They inventors did not detect any effect of Clec11a on boneresorption (FIG. 5K). MicroCT analysis showed that cortical boneparameters in the femur diaphysis were not affected by rClec11ainjection in these experiments (FIGS. 10A-10F). rClec11a thus promotesosteogenesis in wild-type mice in vivo.

rClec11a Administration Prevents Osteoporosis.

Ovariectomy in adult mice is a widely used primary osteoporosis modelmarked by increased bone resorption and bone loss (Rodan and Martin,2000). The inventors ovariectomized mice at 2 months of age thenadministered daily subcutaneous injections of recombinant humanparathyroid hormone (PTH) fragment 1-34, rClec11a, or vehicle for 28days before analysis by microCT. MicroCT analysis showed that thetrabecular and cortical bone volumes were significantly reduced inovariectomized mice (FIG. 6A, FIG. 6B, and FIG. 11C) along withsignificantly reduced trabecular number (FIG. 6C) and significantlyincreased trabecular spacing (FIG. 6E). Daily administration of PTH toovariectomized mice significantly increased trabecular bone volume (FIG.6B) and trabecular number (FIG. 6C), while reducing trabecular spacing(FIG. 6E). PTH also significantly increased cortical area (FIG. 11C) andcortical thickness (FIG. S4E) in ovariectomized mice. Dailyadministration of rClec11a to ovariectomized mice also significantlyincreased trabecular bone volume (FIG. 6B) and trabecular number (FIG.6C), while reducing trabecular spacing (FIG. 6E). However, rClec11a didnot significantly affect cortical area (FIG. 11C) or cortical thickness(FIG. 11E) in ovariectomized mice. rClec11a can therefore prevent theloss of trabecular bone in ovariectomized mice, though it is not clearwhether it can prevent the loss of cortical bone.

Consistent with the fact that ovariectomy increases bone resorption(Harada and Rodan, 2003), the urinary bone resorption markerdeoxypyridinoline was significantly increased in ovariectomized mice ascompared to sham operated controls (FIG. 6F). Administration of rClec11aor PTH did not significantly affect deoxypyridinoline levels (FIG. 6F)or numbers of osteoclasts (FIG. 6G) in ovariectomized mice. However,based on calcein double labeling and histomorphometry analysis in thefemur metaphysis, the trabecular bone formation rate (FIG. 6H) and thenumber of osteoblasts associated with trabecular bones (FIG. 6I) weresignificantly increased by rClec11a or PTH administration. rClec11a thusprevented the loss of trabecular bone in ovariectomized mice byincreasing the rate of bone formation.

The inventors also assessed the effect of rClec11a on a model ofsecondary osteoporosis in which bone loss was induced in mice bydexamethasone injection, mimicking glucocorticoid-induced osteoporosisin humans (McLaughlin et al., 2002; Weinstein et al., 1998). Dailyintraperitoneal administration of 20 mg/kg dexamethasone for 4 weeks inmice significantly reduced lymphocyte numbers in the blood withoutsignificantly affecting neutrophil or monocyte counts (FIGS. 12A-12D).MicroCT analysis of the distal femur metaphysis showed significantlyreduced trabecular bone volume and thickness in thedexamethasone-treated as compared to vehicle-treated mice (FIGS. 7A-7E).Treatment of dexamethasone-treated mice with PTH significantly increasedtrabecular bone volume, trabecular number, and trabecular thicknesswhile significantly reducing trabecular spacing (FIGS. 7A-7E). Treatmentof dexamethasone-treated mice with rClec11a also significantly increasedtrabecular bone volume and trabecular number while significantlyreducing trabecular spacing (FIGS. 7A-7E). Dexamethasone treatment alsosignificantly reduced cortical thickness but neither PTH nor rClec11arescued this effect (FIGS. 12E-12J).

Consistent with the fact that dexamethasone treatment reduces boneformation (Harada and Rodan, 2003), the rate of trabecular boneformation based on calcein double labeling (FIG. 7F) and the numbers ofosteoblasts associated with trabecular bones (FIG. 7G) weresignificantly reduced in dexamethasone-treated as compared tovehicle-treated mice. Administration of PTH or rClec11a significantlyincreased the trabecular bone formation rate (FIG. 7F) and the number ofosteoblasts (FIG. 7G) in dexamethasone-treated mice. As expected,dexamethasone treatment, or administration of PTH or rClec11a, did notsignificantly affect deoxypyridinoline levels (FIG. 7G) or osteoclastnumbers (FIG. 7I). rClec11a thus prevented the loss of trabecular bonein dexamethasone-treated mice by increasing the rate of bone formation.

To test whether administration of rClec11a can reverse the osteoporosisthat has already established, the inventors performed ovariectomy in 2month-old mice and waited for 4 weeks before they subcutaneouslyinjected PTH (1-34), rClec11a, or PTH (1-34) together with rClec11adaily for another 4 weeks. Injection of rClec11a in ovariectomized micesignificantly increased the trabecular bone volume and trabecular numberwhile significantly reducing the trabecular spacing in the distal femurmetaphysis as compared to ovariectomized mice injected with vehicle(FIGS. 13A-13F). Co-injection of PTH (1-34) and rClec11a showedsignificantly increased trabecular bone number as compared to PTH (1-34)injection alone (FIG. 13C), suggesting that PTH (1-34) and rClec11amight have additive effects on osteogenesis.

To test whether human Clec11a has similar osteogenic effects as mouseClec11a, the inventors first added recombinant human Clec11a (rhClec11a)to human mesenchymal stem cell (hMSC) cultures and found that itsignificantly promoted osteoblast differentiation (FIGS. 14A and 14B)and mineralization (FIGS. 14C and 14D). Next, the inventors transplantedhMSCs into immunocompromised NSG mice in hydroxyapatite (HA)/tricalciumphosphate (TCP) particles. Treatment of the mice with rhClec11 by dailysubcutaneous injection for 4 weeks significantly increased boneformation in vivo by the hMSCs (FIGS. 15A and 15B). Human Clec11a thuspromotes osteogenesis by human cells in culture and in vivo.

Example 3—Discussion

Our studies have identified a new osteogenic factor, Clec11a, which actson osteolineage cells to promote the maintenance of adult bone mass. Ourdata indicate that Clec11a is necessary and sufficient to promoteosteogenesis in culture and in vivo. Clec11a deficiency significantlyreduced bone volume in both limb bones and vertebrae of adult mice(FIGS. 2A-V). The observation that Clec11a is required for themaintenance of the adult skeleton is consistent with Clec11a expressionby LepR⁺ bone marrow stromal cells, which include the SSCs that generatemost of the osteoblasts produced within adult bones but which do notcontribute to the skeleton during development (Zhou et al., 2014).Nonetheless, Clec11a is also expressed by osteoblasts and it will remainunclear precisely which osteolineage cells are regulated by Clec11auntil the Clec11a receptor is identified. Beyond LepR⁺ cells andosteoblasts, it is also possible that Clec11a acts onOsterix-CreER-expressing bone marrow cells (Mizoguchi et al., 2014; Parket al., 2012), Osterix-CreER expressing periosteal cells (Maes et al.,2010) and/or Gremlin-CreER-expressing bone marrow cells (Worthley etal., 2015).

Clec11a protein was detected primarily around trabecular bone and in thematrix of cortical bone (FIGS. 1D-F). It appeared to be more highlyconcentrated in some regions of bone than in others. The antibodystaining appeared to be quite specific because it was not observed inClec11a^(−/−) mice (FIGS. 1D-F). These data raise the possibility thatClec11a preferentially acts on osteogenic progenitors within certainregions of bone. Indeed, Clec11a deficiency and rClec11a administrationhad more acute effects on trabecular bone as compared to cortical bone.Nonetheless, Clec11a protein was strongly detected in cortical bone(FIG. 1F) and although Clec11a deficiency did not significantly reducecortical bone in 2 or 10 month-old mice it did significantly reducecortical bone in 16 month-old mice (FIG. 9A). Moreover, Clec11adeficiency significantly reduced the mechanical strength of femurs at 2,10, and 16 months of age (FIG. 9I and FIG. 9J), raising the possibilitythat Clec11a regulates the biomechanical properties of bone independentof effects on bone volume. Administration of rClec11a for 28 days didnot significantly affect cortical bone thickness (FIGS. 10A-F, FIGS.11A-F, and FIGS. 12A-J), but it is possible that longer-termadministration of Clec11a would. It is also important to bear in mindthat Clec11a expression may be much more widespread than detected byanti-Clec11a antibody staining. Secreted factors are notoriouslydifficult to detect by antibody staining, so low levels of Clec11aprotein in the cells that produce it may not be detected. Antibodystaining may only be evident in areas of bone matrix where Clec11aprotein is concentrated.

Previous studies showed that osteocalcin, an osteoblast-derived bonematrix protein, can act as a systemic hormone to regulate insulin levelsin the pancreas after being released into the blood during boneresorption (Lee et al., 2007). Since Clec11a can be detected in both thebone and plasma (Ito et al., 2003), it is possible that Clec11a alsoacts as a feedback signal to promote osteogenesis after it is releasedfrom bone.

Phylogenic analysis showed that Clec11a is most closely related toTetranectin (also known as Clec3b). Tetranectin expression increasesduring mineralization by osteogenic progenitors in culture andoverexpression of Tetranectin in PC12 cells increases the bone contentof tumors formed by these cells in immunocompromised mice (Wewer et al.,1994). Tetranectin deficient mice exhibit kyphosis as a result ofasymmetric growth plate development in vertebrae (Iba et al., 2001);however, it is unknown whether Tetranectin is required for osteogenesisin vivo. Although Tetranectin is found in both cartilaginous fish andbony fish, Clec11a is only found in bony fish and higher vertebratespecies. This suggests that Clec11a evolved in bony species to promoteosteogenic differentiation and mineralization. Among mammals, Clec11a ishighly conserved: the human and mouse Clec11a proteins exhibit 85%identity and 90% similarity.

Although human Clec11a has been shown to promote colony formation byhuman hematopoietic progenitors in culture, the inventors did notobserve any hematopoietic defects in Clec11a^(−/−) mice. Nonetheless, itis possible that Clec11a regulates some aspect of hematopoiesis undernon-steady state conditions, such as in response to a hematopoieticstress. Future studies will be required to assess this.

All of the compositions and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the compositions and methods of this disclosure havebeen described in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to thecompositions and methods, and in the steps or in the sequence of stepsof the methods described herein without departing from the concept,spirit and scope of the disclosure. More specifically, it will beapparent that certain agents which are both chemically andphysiologically related may be substituted for the agents describedherein while the same or similar results would be achieved. All suchsimilar substitutes and modifications apparent to those skilled in theart are deemed to be within the spirit, scope and concept of thedisclosure as defined by the appended claims.

VI. REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

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What is claimed is:
 1. A method of increasing bone strength, volume,mineralization or density in a human subject in need thereof comprisingadministering to said subject human C-type Lectin Domain Containing 11A(CLEC11a), wherein said human CLEC11a comprises the sequence of SEQ IDNO: 10, wherein the subject has not been diagnosed with primary ormetastatic cancer, and wherein said subject suffers from osteopenia,osteoporosis, bone trauma, bone fracture, or is in need of a spinalfusion, or is in need of a dental implant.
 2. A method of treating abone trauma, disease or disorder treatable by enhancing bone formationin a human subject comprising administering to said subject human C-typeLectin Domain Containing 11A (CLEC11a), wherein said human CLEC11acomprises the sequence of SEQ ID NO: 10, and wherein the bone trauma,disease or disorder is not primary or metastatic cancer.
 3. A method ofpromoting bone formation or osteogenesis in a human subject in needthereof comprising administering to said subject human C-type LectinDomain Containing 11A (CLEC11a), wherein said human CLEC11a comprisesthe sequence of SEQ ID NO: 10, wherein the subject has not beendiagnosed with primary or metastatic cancer, and wherein said subjectsuffers from a bone trauma, a bone disease or a bone disorder.
 4. Amethod of reversing bone loss in a human subject comprisingadministering to said subject human C-type Lectin Domain Containing 11A(CLEC11a), wherein said human CLEC11a comprises the sequence of SEQ IDNO: 10, wherein the subject has not been diagnosed with primary ormetastatic cancer, and wherein said subject suffers from osteopenia,osteoporosis, bone trauma, bone fracture, or is in need of a spinalfusion.
 5. The method of claim 1, wherein said human CLEC11a isadministered systemically.
 6. The method of claim 1, wherein said humanCLEC11a is administered locally to a site of bone in need of treatment.7. The method of claim 1, wherein said human CLEC11a is administeredintravenously, orally, subcutaneously, intramuscularly, topically, orintra-articularly.
 8. The method of claim 1, wherein said human CLEC11ais administered more than once.
 9. The method of claim 1, wherein saidhuman CLEC11a is embedded in a slow release delivery vehicle.
 10. Themethod of claim 1, wherein said human CLEC11a is embedded in a polymericdelivery vehicle.
 11. The method of claim 1, further comprisingadministering said CLEC11a in combination with a second bone therapy.12. The method of claim 3, wherein said bone trauma, bone disease orbone disorder is a fracture, osteoporosis, osteopenia, periodontaldisease, or involves transplant/reconstructive surgery.
 13. The methodof claim 12, wherein said transplant/reconstructive surgery is spinalfusion.